Just the frame rails and crossmembers would be mortise and tenoned.
CR — I like the roll-up part but there could be a corrugated metal ridge cap to store the two sides under. The canvas could roll down to the bench or all the way to the ground.
That's all down the road. Right now I'm comparing prices of dimensional Fir and glu-lam beams (2.5X $$$). Maybe the first one will be a cheap proof-of-concept. Scale this up to 6ft floor and move the axles to the middle:
