Janos, Just where do you take Mastery of Madness and Twilight Denizens from? Your acronym pointed me to Player's Guide to Eberron, but that is obviously wrong, as those feats don't appear in that tome's index.
I'm not sure I agree about Extend, as the higher spell slot makes it a trade of getting a weaker creature in exchange for having it stay longer, and my experience tells me that if you really need summoned help, you'll get more use from powerful creatures than from weaker ones, unless it's for destroying really low end foes. And what in heck do you expect a twinned summon to do for you? unless you're facing a spell caster who might try to dispel the summon or otherwise banish your creatures, and you really NEED your summoned beasties to stay, the +4 slot just makes it too costly to be interesting, given the ratio of what you'll be able to summon over what you are going to meet.
Arcane Thesis, Rapid Spell and Mobile Spellcasting, Free Rapid, Extend, or even Enlarged... wow... That's another big lot that I can't remember at all where they are from (and I've checked my usual volumes... PH, complete series, a couple FR ones... but none of those in my library. In the same vein, could you please remind me where the bard beguiler is from?.