There have been some interesting suggestions, Howa 1500, Mauser '98, Mauser '96, K31... I bet theat someone suggested a P-14, and I just missed it.
How about something for everyone? Make a stock, maybe something like the LSS, but the center-section, where the action bolts-up, delete it.
Then make center sections for the individual actions. With all that fancy CNC stuff, I'd think it would be possible to make some precise and robust dovetails that will be nearly as strong as billet and would only require small machine screws to lock everything into position.
Or... Keep the center-section deleted, and go to barrel-blocks to hold the barreled actions.
And as long as we are "dovetailing" stuff together, those guys that want longer forends, just sell them longer chunks that dovetail onto the chassis.
I'm not saying these ideas are perfect, I can see the barrel-block idea being kind of tough for a repeater, for instance and none of these will work for a Lee Enfield.