Maybe there will be a classic spellcasting module, I would buy that.
Definitely, but there are some great ideas on these boards - @
GMforPowergamers' proposal is an interesting alternative. I for one (even as DM) miss the quadratic approach to spells but I can live without it and we have found a way around that - through setting and some other ideas.
For instance the Fireball spell is relatively weak, in my opinion, but because our group has opted for an E6-like approach to 5e it works. I mean if you have limited hit points the higher spell slot fireball (even Sleep spell) becomes pretty potent. Hit Point limitation "fixes" so many things.
As for too many/too few spells.
Cantrips - we have limited them to level + con modifier between short rests. Casting more than the allotted number has a chance to start eating into your memorised spells...with physical repercussions if you go overcast.
Rituals (1) - We have changed HD to Surges (prefer the name), dropped the number you receive and have Rituals cost Surges. Surges represent Willpower & Reserves. So you use them to cast Rituals, gain Hit Points between Rests and expend one to gain Advantage on a check, hit roll or save (reflects desperation).
Casting more Rituals when all your Surges have been expended would incur Hit Point loss.
So essentially a Wizard is unlimited until his physical energies run out. It makes more sense to us.
Also if you introduce things like Casting Time & Spell Disruption, Spell Failure, Material Components, Spell Preparation Time - that may start limiting the number of spells the Wizard potentially has. I prefer they started out with as many as they do, because if you want to tack on one of those spell-casting modules you don't have to balance it out with giving the Wizard even more spells.
Regarding the OP - that a Wizard has too few spells
Rituals (2) - I'm pretty sure the final product will have an increased number of ritual version of spells, thereby increasing the number of spells a Wizard potentially will have. There are several higher level spells which I have spotted which could easily have a Ritual version for them.
And even if they don't, I would probably make one

That's where some of the 4e books come in handy.