Just require that bards use their standard focus (a musical instrument) and call their spells songs. That's a done deal to convert spells into songs and consider rituals and cantrips as bard spells. The only thing the progression chart does is simplify a progression standard and multi-classing. The elegance of the system is that unifying that one resource allows for a much or as little of each aspect (songs vs spells) as desired by the player.
There is no difference between x songs + y spells = z songs and spells from (x + y) songs and spells = z songs and spells. It's all in how a person chooses to imagine and portray it. The bard class doesn't seem powerful. It seems versatile and highly customizable, and that's why I believe it's popular.
As for other methods, a person could simply disallow the class and require players to build the concept from other classes. There are a lot of ways to build the class whether it's from background and feats on another class or multi-classing.
I don't think people should confuse some variations of bards with representative of the entire concept either. Bards were always close to full casters in that they used their class level as their caster level when caster level was still a thing, as opposed to paladins and rangers who generally used half or subtracted from when they first learned spells. Other spell casting classes also did not have 9th-level spells until 3rd ed so it's a mistake of bias to consider 9th-level a requirement of full casting when it wasn't true in 1e, 2e, 4e (because progression was standardized to aedu). BECMI didn't follow up to 9th level spells, and 1e and 2e restricted clerics to 7th level spells to illustrate what I mean. Using the 2e example, bards had the fastest xp table and bonus xp from everything so they advanced fast, but kept full caster level, and only capped out at 6th level spells as opposed to 7th level spells like clerics, and with the mage spell list for much better offensive spells. Bards were serious spell casters compared to priests in 2e. In 1e they were more of a prestige class, but the bard levels still followed druid spells and used full caster level through the list for pretty solid spell casting. That list also combined cleric spells with more offensive spells, much like we would see in 3e and beyond.
All in all, bards were pretty close to clerics and druids as spell casters in pretty much every edition, including 5e where other classes get bonus abilities pertaining to spell casting and bards do not (going with bardic inspiration and skills instead). When the OP states not wanting a full spell casting bard what I really see is a desire to use 3.5 structure for bards instead. We tried that during play testing but the structure was awkward and the song buff was too powerful. Feedback led to what I consider a much better and easier to implement bard model by simplifying the songs and spells into a single resource. A move back in that direction would be a move towards what was tried and rejected, so house ruling or DM recreation makes more sense for those who preferred that style.
The "bards are buffers" idea also wasn't really strong until 3x versions. The inspiration didn't exist in 1e that I recall, and 2e used an odd mechanic that was time consuming before a fight. 3x ed bards did get a few song buffs and more spell like abilities with songs but subsequent editions didn't follow that format either. What 3e did was take a lot of spells, relabel them into different spell levels per class so bards still got access to some of the highest level spells, and filled in the lower number of spells cast/known by using songs known and used (listed as supernatural or magical mostly) so the bards were still highly magical like other spell casters just using a different structure. PrC's expanded on that so we had our snowflake dancers and sublime chords who had plenty of capability plus more skills.
What I like about the current structure is that I can make a lot of different bard concepts very easily with it. I want Gandalf (who's character was based on a mythological bard, btw) I can make Gandalf. If I want Merlin (who was also based on a bard) I can make Merlin. If I want Taliesin I can make Taliesin. If I want Brom I can make Brom. Or Orpheus, or Pythagorus, or The Bard from Bard's Tale. I can make a Constantine bard if I want (he did start in a band and has been accused of stealing magic). They might not be exact but the general concept and approximation is possible. The flexibility of the system used is what makes it a good system for a class from which a lot of forms of inspiration draw.
It's not that hard to make a bard to play similarly to previous editions either. Examples:
1e) Valor bard with thief background who focuses on druid/nature themed spells; or MC fighter/rogue/druid to concept.
2e) Lore bard focused on DEX and skill selection who focuses on wizard spells; or Arcane trickster with entertainer background and inspiring leader feat; or MC wizard/thief to concept same background and feat.
3e) Lore bard focused on whichever ability score desired to fit a previous 3e build concept who focuses on enchantments, illusions, healing, and spending extra secrets on bless and crusader's mantle; or MC 2 rogue levels to offset leveling progression and take a suitable cleric with domain to match concept, and entertainer background.
4e) The structure of the edition using standardized power progression and powers means a person is pretty much taking what most closely matches the previous bard concept.
The important thing to remember is it's a role playing game and the character concept is what's important. The mechanics behind it are just tools used to create the character concept and there's only an issue if the concept a person has in mind is a struggle to create through the existing mechanics or reflavoring existing mechanics as a secondary option. This isn't the case for bards. It's easy enough to create a variety of bard concepts. The mechanics won't match up to older versions the same but the concepts remain.
What I do agree with is in increasing the number bard spells that cover some more of the various bard aspects and flavors. A few more unique spells can increase the flavor and ability to match previous concepts better, and increase the opportunity cost on magical secrets.
Sorcerer "power" only lets them nova more often. That and a little more damage (very little) -contrast with the better ac, hp and more skills + expertise bards get on top of ritual casting-. Sorcerers and bards share about little less than half their spell lists (54 spells), on top, Bards share 33 spells with wizards that sorcerers don't. And they have even more variety of spell effects sorcerers can't hope to share. (and most of those sorcerer spells are basically damage, damage and more damage, but if a bard wants to do damage, they can just take whatever good sorcerer spell they wish.) Replace a sorcerer with a bard and the same party does better.
I disagree.
Wild mage functions differently with some decent options in the subclass ability, while draconic sorcerers already add hp and AC to match bards better. More skills isn't that impressive (especially when sorcerers have access to enhance ability as well, unlike wizards) and expertise is pretty limited. It's a case of skill benefits plus bardic inspiration compared to sorcery points, font of magic, and metamagic. That means the sorcerer can cast more spells in a day and can cast more effective spells than bards' unmeta'd spells. The skill benefits tend to be less impacting than metamagic and/or more spells cast in a day. That's also true for bardic inspiration, but bardic inspiration carries more impact than skill bonuses. You seem to be confusing smaller benefits used more often with bigger and better peak moments and seeing more often as better when the grass is usually greener on both sides of that fence.
Ritual casting is not bad but the spells that can be cast as rituals aren't that potent, the bard still needs to acquire them with opportunity costs (worst ritual caster ability among them all), and is flat out weaker than a feat that any character can take (including sorcerers).
You are also over-selling magical secrets. Bards as a class get magical secrets 3 times and not until 10th level and higher for a total of 6 spells known by epic levels. It doesn't matter how many spells a bard's spell list shares with another class because bards don't get to cast every spell from that list or every shared spell. What matters is how many more spells a bard knows than a sorcerer. It's eventually only 7 spells known and a heck of a long time to get there. It's not like a bard can just casually take whatever spells he or she wants. Until 10th level, a bard knows all of 2 more spells than a sorcerer and they are all restricted to the bard list. Conversely, the sorcerer knows 2 more cantrips which can be used at will, unlike the bard who still has the same number of spell slots per day as that sorcerer at best (ie ignoring font of magic) and still not as well because of subclass abilities and metamagic. Your complaint really only applies to high level play after the sorcerer was substantially better right off the bat with the cantrips and most of the way there with metamagic, and still ignores the fact that those higher levels includes higher level spells to which metamagic also may be applied. That means metamagic's value continues to improve with each new spell level also gained.
The big draw for lore bards is being able to use cutting words as a reaction (the reaction instead of a bonus action is the best part of that ability) and without needing someone on whom to use bardic inspiration dice, and extra secrets because getting 2 more spells known faster helps a lot when gained even if it's a small difference in the end.
All in all, it looks like a pretty good trade off to me. Metamagic is that good.
