Answering upside down ...
Half-Giant 1 = No , but Wish can certainly power a racial level conversion via complicated blah blah blah
Long answer is No, too.
But, if your DM thinks HG1 is weaker than 2 9th level powers (and he should) then it won't break your game to go ahead and do it.
The idea being HG 1 / Psion 19 is not as good as Psion 20.
The very long argument that you can is based on Wish + Savage Species + PHB2 Rebuilding + CPsi racial levels + tricky wording,
and none of the boards recognized bug names participated, nor signed on to it ... so YMMV.
If you use La buy-off, this point is moot. You'll end up sometime around 12th level, without the La anymore, or the exp loss.
The math is complicated.
Erudite Spell to Power converts spells into psionic powers. There's no caster level any more. Sorry.
Consumptive Field does work with this last bit.
Dragon #349 has some feats for Psionics.
Psiotheurgist feat connects one School with one Discipline. Pre-req is Spell Focus (x) feat.
This connects psionic ML increases to psly4mne's increasing Caster level thread.
The basis is Wizard 3 / Psion 3 / Cerebremancer 10, but there are better combo's ... especially early entry stuff.
http://www.d20srd.org/srd/psionic/psionicPowersOverview.htm#disciplineSubdisciplinehas each Discipline school equivalent.
It allows CL + ML = new CL, and ML + CL = new ML , but only in the one school/discipline link.
Wiz 1 early / Psion 3 or Ardent 2 / Mind Mage 10 in carnivore's guide / Cereb 7 or 6 , with psiotheurgist works.
Cleric 1 early / Ardent 2 / Psychic Theurge 10 / Monastic Servant of Auppenser 7 (google), with psiotheurgist also.
Otherwise there's the Wilder, and the short list of psi/magic transparent items in the XPH ... not much.