How would you feel if spontaneous casters got all their spells known for a spell level when they got that spell level?
Example would be that a 1st level sorcerer would have 5 spells known(not including bonus spells from class features, feats, etc.). Then when the sorcerer got to 4th level he would get 5 2nd level spells known, 4 3rd level spells known at 6th, etc.
At least this way you wouldn't need a chart to keep track of spells known.
That gives them a whole lot of power and lessens the excitement of getting a new level. If I had to improve spontaneous casters I'd just knock their spell progression up to what prepared casters get, rather than one level later. It always struck me as strange that they're a level behind.
I agree that it would reduce the excitement of levels where you don't gain the next level of spells. This would be even worse for classes that don't get 9 levels worth of spells as they go for longer before getting the next level. I mean look at mediums, they don't get 2nd level spells until 7th level and then gain new spell levels at a rate of 1 new level every 3 character levels before capping out at 13th level. Currently they get at least 1 new spell known at every level.
Not only that but having to suddenly pick 6 spells when a spontaneous caster does gain a new spell level would be kind of daunting. What if they choose a spell they end up never using?
Edit: I have a hunter in a current game and he has spells known I've yet to use and if things keep going the way they are I might never use them. I didn't make bad choices just the situations I would use them in have yet to warrant their use. Plus I end up burning most of my spells outside of combat casting cure light wounds to help patch people up. I have yet to cast lead blades or Residual Tracking. Heck, I can cast enlarge person once per day and in 5 levels I've only used the spell twice.
There is already 1 spontaneous caster class that follows a progression similar to this... the Occultist... at each level that they obtain a new spell level they gain a new spell known for each implement they have... and each time they gain a new implement they learn a new spell known in the spell school tied to that implement for each level of spell they can cast...
This does give them a whole lot of flexibility with their new spells especially at mid-late game when they are getting those 4+ spells off the bat... and the gap between spell levels is very in eventful... it gets even worse when you realize you took a spell you will almost never use and had a different option that would have been so much better... and often times the factors that influence spell choice can happen in a later session after you already have that level of spell.
You might also want to revisit how often the player can swap out spells known. While gaining a new level of spell is a major reason for wanting to do that, being stuck with bad initial choices for multiple levels is also not desirable.
There is already 1 spontaneous caster class that follows a progression similar to this... the Occultist... at each level that they obtain a new spell level they gain a new spell known for each implement they have... and each time they gain a new implement they learn a new spell known in the spell school tied to that implement for each level of spell they can cast...
Yeah take a look at the Occultist, I love it but it's different.
Look at it from levels 6 to 13.
At level 6 they get a new implement, so they get 3 new spells (levels 0, 1, 2).
At level 7 they get a new spell level, so they get 4 new spells (all level 3).
At level 8 they get no new spells.
At level 9 they get no new spells.
At level 10 they get a new spell level, so they get 4 new spells (all level 4) AND they get a new implement, so they get 5 news spells (levels 0, 1, 2, 3, 4) for a total of 9 new spells.
At level 11they get no new spells.
At level 12 they get no new spells.
At level 13 they get 5 new spells (all level 5).
(After that it's a bit normal)
Now this isn't necessarily a problem, but it's definitely a mostly-dead zone with a huge benefit right in the middle.