Spell-less subclasses for Paladin, Ranger, Bard.
I guess a spell-less Bard would be a Minstrel.

I could definitely see an Oath of Fealty for a Paladin who was a non-magical Knight in the most traditional sense, but still able to do (EX)traordinary (yeah, 3.5 reference) things due to his preternatural devotion to duty.
Or a 3e fan, given the incarnate, healer, archivist, dragon shaman, beguiler, duskblade, warmage, soul knife, wilder, and swashbuckler weren't updated to 4e.
Even obscure as those are, some got treatments. The swashbuckler and Beguiler got PPs and dragon articles, PPs made a small attempts at incarnate, healer, themes or backgrounds could suggest swashbuckler, healer, archivist, and there was a wilder theme, duskblade was just another 3.x stab at a gish, and 4e also had plenty of those, any arcane striker could probably claim 'warmage' (it was another mechanics-differentiated class)...
... I wouldn't expect any of those to have been satisfying, but given more than 2 years (ie no Essentials re-boot), I'm sure they could have been tackled better eventually. And, of course Pathfinder was there within a year to continue those classes and add ever more, as well.
So, even though there's no expectation of 5e ever being as option-rich as 3.5, it's still no comparison, really.
Within 10 months, 4e had every class that had appeared in a prior PH1, plus a few from more obscure sources, plus some completely new ones.
We're over a year into 5e and it hasn't even covered everything that's been in past PH1s.
Not to offend or insult but...
I hear the phrase "I can't see any new classes for D&D. The current one do pretty much everything." in some form or another in D&D forums a lot.
And I wonder how creative or imaginative the fanbase is. Is it:
"No other classes fit in D&D"
"No other classes fits in my image of D&D"
"I can make almost any other class using what we have."
or
"I just can't think of any other classes."
If we got creative enough (and were charitable enough about meeting concepts with very tenuous modeling and depending on lots of generous DM rulings), we could probably build any concept with MC'ing and a Fighter, Cleric, & Magic-user class. (Even the Rogue would just be a light-fighter with a background and a lot of skills.)
It'd take that level of squinting and settling to do a lot of concepts with the current classes. 5e devotes a lot of sub-classes (~30 out of 38) to doing this or that caster-concept (some of them little more than meta-game concepts) just so. It could do with more classes and sub-classes to handle other sorts of concepts.
With regards to the recent kerfuffle about Warlords, for example, my feeling is that introducing them really just tends to limit what Fighters can be - as in the Fighters can only be grunts
The design of the Fighter class limits what the fighter can be. It can be DPR. It can add a few tricks, it can even
actually cast spells, but those tricks are really only viable so far as they support that main function. The 5e fighter is a beatstick, a very good beatstick, and one available in several styles, but still a beatstick. Trying to shove it into any other function renders it sub-optimal or even non-viable.
Which, is not, by itself, a bad thing: It's strongly reminiscent of the 2e fighter, which was a damage king, and exactly what a lot of folks want out of the class.
With the fighter so much more limited than it was in 3.5, and there being so few non-supernatural sub-class options (only 4-5, among Fighter, Rogue, and maybe, Barbarian - out of 38 sub-classes among 13 classes in total), new 'martial' classes are a must.
The Warlord is the obvious one to start with, since it was in a prior-ed PH1, and can fill the critical 'healer' role (even though it never literally healed, just restored hps via inspiration), enabling functional parties even in low/no- magic settings.
Then there's the Scout from 3.5, a more militant/wilderness rogue.
Then there's all the interesting/fun/crazy builds you could do with a Fighter in 3.x/PF...
...and the one you couldn't: a Defender, like the 4e Fighter, or 3.5/Essentials Knight or the 3.x Devoted Defender/Dwarven Defender/etc PrCs...
..then there's Bo9S.
A Duelist/Swashbuckler/non-mystical-Martial-Arts-Master might be a good addition, too.
Once we have 4-6 mostly-martial classes in total and 20 or 30 such archetypes, we might consider further over-stuffing the game with yet more casters...
