Horwath
Legend
Spells known is the best limiter.I have time and again seen number of slots brought up as a way to control spellcaster advantages in power and utility. BUT how about using Spell Schools as a control mechanism. Limiting access to 2-3 schools at level one and gaining access to further schools as the character levels up.
To delve further into spell school control would be the idea of minor and major access ie minor access being spell levels 1-4 and major access 6-8. Even this can be further manipulated by changing the level spread or introducing an intermediate access.
you can have one caster class with access to all spells and spell known of 2014 sorcerer and it would be balanced. extra known due to sub-class may apply.