Well if you're going to spray mount you have departed from strict archival squeaky-cleanness, so you might as well use Gatorfoam which is much like foamcore but a great deal stiffer.
I pay $47 for individual sheets of 4x8, 3/16" Gatorfoam, versus $9 the same size of ordinary foamcore. Or you can just use 3/16" or 1/2" foamcore for sizes like 24x36. BTW you can also use Masonite ($10/sheet). A lot of framers would use Scotch 77 spray for that kind of application...that's not an endorsement, just an observation. I like to roll Muck on the board with a paint roller and lower the print onto that...use an assistant or tape down one end on the worktable first. The print should be pre-coated with ClearShield or Glamour or some coating that has had enough drying time so that you can run a cotton gloved hand over the surface to press it down good.
A relatively determined person can cut Gatorfoam with a utility knife. My supplier will cut it for me for free as long as I don't ask for a whole bunch of 8x10's or something. Tables saws work well too, as do the wall-mounted media cutters used by framers.
The only problem with selling board mounted prints to customers is the elegance problem. There's just something pretty Home Depot about a print glued to a board. If your marketing department can figure out a way to put a good spin on it, then go for it. Frankly, at that point about 70% of the framing work is done, it would not be a huge additional step to slap a frame around it. If you're working in standard sizes there are several suppliers who can sell you really great looking pre-made frames for way under $100 in the 24x36 to 30x40 sizes, I just came back from talking to a bunch of them in Las Vegas.