Since epic progressions of sorcerer and favored soul are pretty terrible, you're only going to want to progress spellcasting by fourteen levels each. That can go down to 12 if you have to, since getting ninths is probably more important than number of slots, given how improved spell capacity works.
Since you're epic, having them for epic spellcasting is all that's really all that matters
So,even if can fill up the gaps in your racial sharn spellcasting by gestalting three levels of sorcerer and favored soul with your racial HD or LA, it's not strictly needed. Instead, consider Factotum1/Battle Dancer 1/Warblade1/something1/wildshape variant ranger 5 (yes, you get no use out of wildshape. It doesn't matter)
After your racial limits are taken care of, you have 42 class levels to distribute, 21 of which can be PrCs. I'll list by PrC since they're exclusive
One possibility:
7 levels of Iot7V (gestalt with favored soul)
1 Level of Ur-priest (gestalt with favored soul or sorcerer, your choice) * Technically, since you're using SLAs, you aren't casting divine spells.
5 levels of planar shepherd (yes, you're taking five levels of wildshape ranger just for this.) (advances ur-priest, gestalt with sorcerer or favored soul).
Advancement just from that :
Sorc 12 (got ninths, take epic spellcasting),FS 8,UrPriest 6
And eight levels of prestige classes left, needed to advance 14 levels of various spellcasting.
And I think I just threw up a little from how much cheese I crammed in. You're tight on feats, but I think you can make it without having to resort to embracing/shunning the dark chaos.