No, please no. I don't want to skill chain -.-;
Those 11 days are over, and I'm glad SC is over. Just imagine trying to save a skill (lowering your overall dps), dodging post heart in Titan EX, and all that for a shiny animation which will be lackluster damage. Heck even ff11 people didn't save tp for SC for a lot of content. Plus with the way our TP works this couldn't happen the way it did then, and if you want it to work differently then you are just asking for another form of LB. Now, if we had a way to make it so each group role in a party had their own special bar to build. That would be cool, then fights could be tuned a bit harder for this extra bonus.
SA is useless because we already have bonus from attacking from behind... called combos.
TA would be bad due to game design considering they would definitely give a new tank job a way to generate threat just as fast as WAR/PLD because otherwise "it would give reason to exclude them from fights." (which happens already ranged/melee - but you know this excuse would be used)
Now, new materia variety sure. I even mentioned before in another post about "melding soul stone" with materia that augments our abilities. "Cheaper medica 2", "Faster Cure 2", "Potent Cure 3" things like that.