I think if the question is, can the track loader push a 6' blade, then the answer is YES.
But the real questions are whether the styles of implement and approaches you're considering will address the problem, and that's more complicated. I don't have much experience in it (i have 99% used my box blade on dirt) but i have seen repeatedly that if you don't rip up (essentially DEcompact) the surrounding material from a low spot, it will always reappear because whatever you put into it cannot form any kind of 'interlock' with the already-hardened walls of that depression, so it stays 'loose' and gets bounced/flung out when driven over, leaving basically the same hole as before.
So i think you need rippers/scarifiers. Again, not a power problem with that machine, but many landplane type implements have no scarifiers. So i think that right there is the next question. Which type of implement could you build or buy that is suited to both ripping and smoothing. Modify a 3pt box blade is cheapest, buy an SSQA box blade is possible, modify a land plane is possible or some might have rippers, or there are other sort of in between designs that have rippers and something like a rake/comb on front.