I don't think snaps will hold. When I suggested it, I was thinking of the usual sort of modesty panel, which goes behind the lacing and can get a bit scrunched around as things get tightened down. If you're actually looking to fasten the garment closed, I would definitely use hooks. Big heavy coat hooks, by preference. (Like
this or
this.) They'll be the easiest thing to get closed and they'll take a fair amount of strain if they're well attached.
I think you'll be able to get a small waist reduction without lacing, but there's a lot of pressure involved in a several-inch waist reduction (60-80 pounds per square inch)
1. Trying to bring that pressure to bear by hand, without the use of a pulley (the laces), is going to be really hard. Putting it on will also be potentially uncomfortable, because you'll have the fastened area at full pressure, with no tapering off to areas of no pressure at all. There won't be the chance to wiggle around at half-tension to get everything settled right.
I'm not saying it's impossible to do at all, and I think it will look really cool if you can pull it off, but it'll probably take a bunch of experimentation. The footnote is a super cool read, by the way. Science!
1 The Corset: Questions of Pressure and Displacement, by Robert L Dickinson. 1887 -
en.wikisource.org/wiki/The_Corset