So, level 10, optimized for whatever, one PrC, all books (with Hyperconscious and Untapped Potential?) and online content, two flaws and one or two traits, standard WBL? How about 42 point buy, to make it easier on the fighter?
Races? LA-buyoff? No crafting, I assume.
Also, just one fighter vs one astral construct? Fighter can't attack the psion, and the psion can't do anything but make a construct and, what, augment it as he likes during the fight? Or can the psion get more involved, so long as he doesn't directly attack the fighter with anything but his construct?
Any other houserules?
Oh, and the arena has to be rather large. Large enough to fit both the construct and the fighter.
[edit] Oh, and I believe I shall give my construct a nice fat Int score...