Nice
I would use a 3 pipe drain if you can fit it still, similar to the bean animal but less complex. First is the main drain flush with the bottom of the weir, this has a ball or gate valve to close till the water level begins to rise. Next a durso which sets the water height in the weir, make it just tall enough to stop splashing noise as water goes from tank to weir. Lastly an emergency, simply a pipe usually set to the bottom of the brace to take the flow if one of the others gets a blockage before you get wet carpet. Being totally open it will make a nice toilet noise to let you know to check it out too.
Use as much hose instead of pipe for your return, will cut down on noise. The larger the diameter the longer the run needs to be to dampen vibration.
Also noticed, depends how much you like your stand maker but you probably don't need the extra cross members under the sump. A piece of 18-24mm marine ply would do the trick for less hassle if you wanted to.
Lastly if piece of mind is a priority (you work away?) I would consider using schedule 80 plumbing. VDL bulkheads and ball valves are the ducks nuts, heavy duty, high quality and real seals so your not hoping a bit of thread tape with hold all that water in. Plus the grey colour tends to blend in nicely.