Good idea about a Nar Demonbinder chassis for an accelerated caster. One thing though - I have a particular distate for prestige classes advancing the spellcasting of accelerated spellcasting prestige classes. I see these prestige classes as particularly focused and unsuited to advancing with another PrC.
Example: wizard, ur-priest, mystic theurge. You get the 9s, but everything about the ur-priest is sacrificed to the optimisation.