So in other words miners make the ultimate decision? If this is the case, then Bitcoin Unlimited is even worse than I initially thought. Otherwise, elaborate what you mean exactly (since everyone can vote via software and miners create blocks).
I do not think that the miners having a lot of power in this decision making process is a bad thing, after all they are the only group that have a direct and lasting incentive mechanism acting upon them to do what is best for Bitcoin. Furthermore this would not just be up to the miners, they would still need to move with the economic majority, this is where the negotiation would take place.
So in other words, BU it is quite similar to BIP100 with the exception that with a combination of rogue nodes and miners the block size could be inflated so much that it would destroy Bitcoin? Don't deny this possibility with weird and not completely relevant to my statements.