What exactly is the "future" that you're saving up for? You're going to need Exceed eventually (and in April, each FLB Merc Axe gives you 50% cap). Exactly how eventually is something that I just don't know, since as a Veteran I was fed all the Exceed weapons by Union events.
I don't know what kind of damage you do right now, but Yori does increase your burst cap with her 3-A skill. It's not a huge amount and re-using it is difficult, but it is there... ... but even if you cap your bursts, Yori's 2-A will make you burst so much more often.
I don't really have a good answer for you. What other Soul were you thinking about?