This is a derivative conversation inspired by THIS
thread. Thanks, Boomwolf, for the inspiration!
As mentioned in Tome of Battle, the Swordsage can, with DM approval, learn a spell instead of a maneuver when available... this is then taken a step further in that any character can learn a maneuver to use once per encounter.. by specifying swordsage as your source, you can then (with DM approval) learn a spell to use 1/encounter. I've got a handy table here to break it all down.
So, non humans get 7 general feats to blow over their career. this boils down to 2 1st level spells, 2 2nd level spells, 1 3rd level spell, 1 4th level spell, 1 5th level spell.
They are usable once each per encounter, unless you spend a feat to earn adaptive style (recommend at level 3) so you spend a full round to "recharge" the spells for use again.
OUTSIDE of combat, it is totally up to the DM how often they can be used, though it can theoretically be used once per 12 seconds... cast recharge cast recharge etc.
Also worth noting: it is generally recommended the spells available be limited to "personal" range spells.. true strike, wraithstrike, fly, featherfall, etc... spells that affect only the caster. Even teleport at level 18 isn't unreasonable... summon monster V, cloudkill, evard's black tentacles... even if you allowed these to be used at level 18... they aren't out of balance... warlock has at-will SLA that are as good or better than these already.
A fighter willing to sacrefice a feat to gain access to True Strike 1/encounter is actually not so bad.... 2 feats to have access every other round... actually, every 3rd round (cast, attack, recharge...) is also VERY reasonable. at level 12 being able to blow a feat to cast fly is not unreasonable either.. you can get boots of flying for mere gold. It's really the nasty stuff like an at-will 6d6 fireball at level 12 that should probably be nixed.... but a 9d6 fireball at level 18? that's getting awful close to just using a cone shaped eldritch blast from the warlock.. and it still can only be used once every other round if the caster is willing to blow a full round action to recharge it... and forsake armor to avoid ACF.
This is a great way to toss in some gishiness, but IMO hardly disruptive.
Debate it if you wish.