You could swap top ends for the 79cc Makita p&c and gain 15ccs. Even better if it's ported. That'd be a very powerful saw. Just swapping with a stock top end would be a pretty cheap way to get a big power bump compared to buying a different saw. Problem is that you don't get to add another saw to the lineup that way.
You lost me on the chains being cheaper and lighter with a 28" bar vs 24". Generally speaking, bars that length run the same types of chain. Anything available for a 28 could also be spun up to for a 24" bar (skip, full comp, semi chisel, etc.).
28" vs. 32" I should have said lighter and cheaper bars and chains. Much on the plate right now.
I'm interested in the larger 79cc top. There are some youtube vids showing the power. Too many current challenges to consider tearing the motor apart.