i recently used a variation of this with a monk fist of zuoken illithid slayer combo, borrowing the tashalatora feat from eberron to get the monk to stack with the is. since fist does grant psionics, so technically the is can advance it, the tashalatora feat pretty much assumes you will only apply it to base classes, not prestige like is. my dm let it slide due to ambigious wording, and i suspect that he either has some stuff in store that will seriously challenge us, or just outright not be very survivable. ^^
there are a few prestige that grant spellcasting, i believe nature's warrior is one, just off the top of my head. i'm sure there others.
