Here are a few ideas.
Solid core doors for bench tops.
Peg board panels framed in poplar to match the bench tops and some of the machine bases. Unseen inside the panels are 1/2" vertical stringers on 6" centers, glued to both the luan "back" and the peg board. The frame has multiple internal rabbits like a picture frame to support the inset back and peg board. No warps or bends with the heaviest loads.
45x25 with segregated shop bay, half bath, walk in storage, heat and AC
R2D2 (ShopVac) sporting dual directionally tunable exhaust, steel shelving unit, Mr. shop press performing dual duty as a clamp rack
Peg board panels and benches. I keep "sacrificial" sheets of masonite on the bench tops most of the time.
The bench with the vice is the same height as the t-saw to serve as an out feed table if need be.
Peg board detail. The poplar screwdriver rack is fitted with peg board hooks so it can live in any spot.
For greasy or oily work the lower bench is also deep enough for one of those "Blitz" (under car) drip pans.