The Free Market needs a change.

That would be a huge strain on merchanting, which Nexon has already recognized as an in-game activity. Many many more people would sell stuff, and alot more of it instead of just the 16 item limit or whatever. So a MTS-version would be cram packed with loads of garbage just like MTS. It would be nearly impossible to scan every page for things to buy for cheap and resell.
Also, some people, like me, don't always know what they're looking for in FM until we find it. Would be really hard to just scan a FM-MTS.

Exactly how would that be when I explicitly specified behaving the exact same way at the exact same costs as the existing NX merchanting based system?
Are thousands of people going to suddenly buy NX just to cram garbage into the new FM? That seems improbable at best and even if they did the whole point of it being in that format would be to quickly wade through the stuff you're not interested in.