I don't think it would be a problem. Like Erdogan said, the miners will use the "tip-toe" method of increasing the block size. Worst case, a large block gets orphaned and nobody tries again for a while. But if the larger block doesn't get orphaned, then the network will assume that that size is now supported (thereby setting a new effective upper limit).
This doesn't put the power directly in the miners' hands. It keeps the power where it already is: in everybody's hands! It just makes it much easier for people to exercise the power they already possess.
I disagree. For example, I would not set my node's limit to anything greater than 32 MB until I understood the 33.5 MB message size limitation better. I expect many people would do the same thing. Rational miners won't dare to randomly publish a 100 MB block, because they'd be worried that it would be orphaned.
Furthermore, since miners would likely use the "tip-toe" method, the effective block size limit will grow only in very small increments, helping to reveal any potential limitations before they become problems.
yes, i've called this "advancing together" but "tip toeing" is even a better descriptor as it implies small baby steps upwards as opposed to random big steps. miners will not only do what's best for themselves but what's best for the group. they know that all hands on deck are needed as a team to replace the existing financial order. where BitcoinXT is going there will be plenty of profits to be had for existing cooperative players as well as new entrants. the stakes are enormous to the upside but individual miners cannot afford to be caught being dishonest or attacking or they will be left behind or severely deprecated ala ghash. what a shame to miss out on being the next JPM as a result of being greedy.