I support misterbigg's idea of miner-voted limit changes, calculated at each difficulty adjustment, preferably with the options "decrease" and "disregard my vote" in addition to "increase" and "keep". I chose "other" since this is a specific proposal.

If this is somehow less feasible than other options, I need someone to explain me why it's so. Maybe 90% is too high a threshold though. With "decrease" option available, a simple majority might be sufficient. Although this would make the fork less smooth, or require an additional forking condition (90% for the first change and simple majority for the rest?)