I see one problem maybe! I know I could barely squezze behind it if I had to work on the plumbing.
I love the detail and effort so far. Sorry If I only mention one small detail as you may not plan for it to be there when it's finished.? I noticed it may have a sump in another room? (hole in the wall!)
I also see three pumps. I assume the iwakis are returns the ?sequence is the closed loop and the internal dolphin (dp2000?) is for the beckett skimmer?? Any refegium in the sump or other plans. I recently saw sompthing that is sweet I wish I had done and that is where the sump was modified at the bottom!!! They made it so that it was ever so slightly cone shaped so they could stir up the sump and drain it out from a ball valve to drain all the crap out of the sump. often it's so hard to work on a sump because of equipemnt size and space constraints..Just a few things to think about...
Your icon looks exactly like the one from Small Colonies .com