Need a Wis of 13, for a Psicrystal to have Metamorphic Transfer, but that is within reach.
I like Reach Spell metamagic adapted, but basically that's two houserules in one, although somewhat reasonable.
I also like using Feat Leech, but only on feats that can be taken more that once, and have no prereqs.
iirc - there were maybe 4 builds at most, that popped up over the years. Maybe Scion's psicrystal guide on the psi-board is still around.
I think a couple were in there.
Snake8 - that's interesting.
Using the Big Guy approach to get to the 21st level psicrystal ability. Minor Problem, the psion can't give the psicrystal a higher level power than he already has. If capped at 5th level powers, that's all the psicrystal can get. Ways around would be: (1) ... gaining temporary knowledge of a higher level power on your list, via the Powerstone nerf near the back of CPsi ; or (2) ... Psicrystal 21st level+ feat takes one of the epic feats that lets you pick up to whatever power level you want to. Tricky. Might need some focus work to get it to work right.
Also works with whatever 21st level feat it can get there. Epic feat early, but not for the psicrystal to use, for the Psion to use. Nice. That's an Epic feat sometime around 12th level, just for the length of the Feat Leech. Still, good stuff.