I just looked back at one of the TGS demos shown by gamersyde.
Two things I noticed.
1) When picking TP to summon Odin(has a 3 TP cost), another command appeared on Lightning's menu(only had 1 TP cost).
Meaning, even though the devs said there would be no limit breaks, there may be some sort of special abilities utilized through TP.
Meaning I may still be able to use my precious Overclock.
2) When picking the summon command a completely different sub menu opens up(with Odin's name in it). Why have a sub menu(with the English word "Summon" on top) when each character only has one summon?
My l'CD theory just seems more and more likely now.
Alternatively it could just be a way to have you party members perform a summoning.