How about getting extra spells based on your ability score for DnD 5e? Let’s see what you think-
Extra Spells
You are a practiced spell caster who is either truly touched by the gods or a master in your own right. Gain an number of extra spell slots equal to your spell casting ability modifier. You may use these to cast one extra spell for each level you can cast spells. You may not use these extra spell slots to cast more than one spell of the same level. As an example, a wizard with an intelligence of 16 could cast three extra spells, and could cast those extra spells at spell levels 1, 2, and 3. But that same wizard could not cast extra spells at levels 2, 3, and 3. When you gain this feat, you must choose a spell casting class that will gain the extra spells.
Thoughts?
Throat Punch Games 
Seems limited and unfair. I would think if you’re high enough, you could cast higher. Why not higher?
I want to keep someone from casting nine extra 9th level spells, so I limited the levels you can cast. Sure, your level 1 magic missile might not do much when you can cast Planer Gate, but with this feat you get one extra planer gate.