Are you looking at any one machine in particular? Do you have any more information about it? Or pictures of it?
I'm thinking of buying a straight lockstitch industrial for FMQ. Because they're so high-speed, you're probably going to have to put a router controller between the outlet and the motor to get the speed down to a manageable level.
If the bobbin is vertical, any lockstitch industrial without a top feed (walking foot, even feed) should work just fine. When I find the one I want, I plan to remove the feed dogs and replace the needle plate with a darning plate - no slots for feed dogs, just the single needle hole.
They pop up on craigslist pretty frequently, with clean tables and machines - at MUCH lower prices than those for new midarm machines.