Corrugated fasteners just do not last over time in anything bigger than 16 x 20-ish. When I did framing we had these little plastic bowties that we pounded into mortises cut specifically for them which pulled the joints tight after gluing. The only time we needed to use additional clamps and/or nails was in cases where the wood was too weak to take the pressure of the bowtie and snapped, or for large mirrors that needed additional reinforcement. Dominos didn't exist back then, but they will definitely work in heavier moldings.
Miter saws used in carpentry were never present in any frame shop I ever set foot in. I believe you could absolutely use a Kapex for that purpose if you wanted to, but I wouldn't want to. What passes for "thin kerf" in carpentry is actually incredibly thick, and it's way too easy for a violently spinning blade to knock a small chip out of the face of a highly figured molding you paid a lot of money for. We always cut ours by hand, but something like a vertical band saw could also work.
I understand you want to try and make this a simple, foolproof process for inexperienced people to succeed at, but the cold hard reality is that it takes a decent amount of skill to frame pictures well no matter what tools you buy. There are fancy laser machines nowadays you can just punch the "double v-groove" button on and get a perfect, overcut-less mat spit out the other side, but that is ultimately a very small part of what goes in to mastering this particular trade. Your work will be scrutinized to a degree that no crown molding is ever subjected to.
By far, the most valuable tools I ever had in a frame shop were sharp razor blades, a wide assortment of felt-tipped pens and an ATG gun. Everything else was more of a nice-to-have.
