A major flaw I've noticed in the system is that if a sorc has heighten spell they get teh effective massive increase to dc that others were warning about. I decided to adapt the idea with a class progression. See what you think.
Version 1:
Force Flare: A 1st level sorcereor (or bard) has learned to at times push his innate spellcasting past his normal limits. Whenever casting a spell make a charisma check (DC 20). On a success, the spell is cast with a +1 caster level.
Force Fire: An x level sorceror has been able to push his boundaries even further. Upon a successful DC 20 charisma check, you gain +2 caster levels.
Force inferno: As force flare, but +3 caster levels.
I didn't think of the level requirements, but they could be balanced as appropriate maybe like 8th for the second, and 17 or higher for the 3rd. It gives an actual reason to stay a sorc to high levels instead of a prc, and it allows them to at times become more powerful than wizards... and allows for some of those epic like damage caps to apply to nonepic games.
This idea could also be adapted to the idea of specialty sorcs, like the iconic elemental sorcs. An example.
Fire specialization: A fire sorc gains a +2 to their charisma check for force flaring when casts fire spells and a -2 to all other spells. OR an extra +1 to caster levels when casting fire and -1 to other spells (so at low levels most spells gain no bonus).
*I like the simplicity this gives but still has a nice "punch" factor. Note that bards gets the first version not the later ones.
Version 2:
Force Flare: A sorc or bard of 1st level when casting a spell makes a charisma check (DC 20). The check is made before the sorc specifies what spell they are to cast. On a success, they may apply any +1 or +0 metamagic feat upon their spell. They do not have to know the feat they are using, but they still pay the cost as normal.
Force Fire: A successful force flare check will allow the sorc to apply any +2 metamagic feat (or a combination of two +1 metamagic feats). In addition, a check of 22 or better allows the sorc to subtract 1 spell level when applying these feats.
Force Inferno: As force fire, but now you can apply any +4 metamagic feat or combination of lower ones. Also, a check of 25 allows you to subtract 2 spell levels.
Perfection: A 20th level sorceror has honed their innate talents to where at times they are a true extension of their hand. When a 20 is rolled on a force flare check, the sorc may use the quicken spell feat without a change in level and without a change in casting time. You cannot use this ability and the other force flare abilities at the same time.
Specialization example: A fire sorc gains a +2 to charisma checks for flaring all fire spells but a -2 to other spells.
*This version gives a blend of flexibility and power. It allows the sorcs to have true bredth of flexibility, but you still have to pay for it. I also gave it a dual mechanic, in that "weaker" sorcs still get goodies (the flexibility) but the more powerful sorcs get a little extra (the lower spell requirements).
