A small exchange doesn't need an automated system to deal with tx mutability. We don't. That is because 99.9%+ of the tx will never be mutated.
We'll see who sinks and floats as other exchanges pick up the slack and grow.
I wish you and them all well, but I would be surprised if there aren't other noteworthy casualties.
And anyway, this is a good opportunity to improve things, assuming the devs act on it. Otherwise, it'll just generate bad press.