Time: The gule is set in about 1/2 hr, but it usually sits for 2 hrs or more (like overnight. We try to do them at the end of the day.
Space: I count 17, 4 x 8 foot tables at the moment.
Take away one each for joining, matting, mounting, joining, packing, shipping, and 4 for fitting, that leaves 8. OK, take away 3 more for misc crap, and we still have 5 clear open spaces that see service as needed: More fitters, stacked materials for large jobs, oversize orders (we have 1, 8 x 16 work area, and 2, 8 x 8 areas if needed).
I like to have the shop organized in space that can be cross utilized as needed. So space is not a problem.
But if you don't have open space in your shop, them something that takes up space for any given amount time might not be a good product or service to offer.
Hot glue: Not stong, a more temp bond. Also, since it is usually a laarger (as in poster) size being mounted in the fashion, the hot glue will be too cool for over half the are to even make a bond by the time you get back to where you started.
White glue, wood glue, pva glue all have much onger open time, or working time.