Finished up the workbench. Made with mostly free 2x4s, with some extra 2x6s purchased.
Half laps everywhere.
Two sjoberg vises because I just have too much money to spend.
Dog holes.
Flip down casters.
Adjustable leveling feet that I designed and 3D printed. You can kick them over with your toe to adjust and get rid whatever wobble appears in that particular spot.
A shelf is a bad idea in a bench - you need easy access to the bottom to adjust clamps all the time. Now an assembly table can benefit from shelves and such - but they don't need the strength this has.
You should be wary of giving universal "bad idea" advice for under bench storage. I have a split top Rubou with a cabinet underneath that's worked great for over ten years now. There's enough room between the top of the cabinet and bottom of the bench top to let in a clamp head.