i guess even taping one of the film positives to the pallet would work.
Old school! That was my preferred method in my early days. We use pre-reg though and it really is best to just pull a key color and flash it enough to reg the rest of the colors without making a big mess.
I like the idea of just printing the reggies with a little bit of plastisol and cleaning it out but, with the pin-lock, we have no reason not to simply load the wb and go, we'll be in reg quick enough, it's only a simple bump left or right that's needed, if anything.
John the "poor-man's pre-reg" you describe is in old M&R manuals. Great method I would say, all you need is a good film template for positioning and a simple alignment board. Cheap as all get out and very effective.