benchwork

One possible solution would be to have some cutouts that you could walk into, this will give you much more access to everything on the table. The track would wind through the canyons.

These could also be liftouts that you could pick up when you needed to access stuff in the back.  You can arrange track to cross with proper alignment pins, it's the same as I have to do for my lift-bridge on my layout.   It'll sure beat climbing on the layout that much for everyday maintenance.

If you make that a solid piece, all the stuff you do on the back will be climbing on the layout, I'd have to think that will get tedious!

Another point, at 30" high, I'd pre-wire everything I could with the benchwork propped up vertical to work on it.  Wiring under a 30" table will be VERY tiring!

All 2x4 is total overkill and it would weigh a ton, in the event you ever wanted to move it. 1x4s would be sufficient. You could probably get away with 1x3s if you build it ladder frame like the image. For legs, either 2x2s or a 1x3 and a 1x2 glued in an L with a block on the bottom for a leveling foot would also be sufficient.