I think I am going to roll a LEGEND "mythic path" I have always wanted to roll an ultra levelled character and while I am going to lose on some very powerful abilities I am sure beating the game is not going to be that difficult anyway. I always wanted to play a good Mystic Theurge and it seams to me a heightened level cap coupled with increased XP wins fills the holes on that prestige class. I am still thinking what I will do once get level 9 spells on both spell lists. Maybe I will splash in some Sneak dice there to follow with Arcane Trickster, another favourite class of mine, but that does seam like trying to do too many different things with a single character.
For a second play through I am leaning on rolling an evil wizard with Lich Mythic Path. An old guy who goes into lichdom for life all eternal, probably Urganthoa(*) follower....
(*) I don't think I wrote it properly but whatever....
Last time I heard, Legend was unable to go past caster level 20. You could go Sorcerer 20/Oracle 20 rather than MT to avoid gimping yourself on caster level in your first class, or go Sorc 10/MT 10/Oracle 10/Vivi 10. The only thing Arcane Trickster would give you is ranged legerdemain and surprise spells.
Honestly, at first glance Legend looks best for Melee or 3/4 BAB characters to get multiple capstone abilities rather than pure casters. Its apparently limited to 4 attacks total, but apparently they can reach +40/+35/+30/+25.