I've largely decided on the sump design, I'm going to enlarge the below uncleof6 design that will provide a 20X24X10 skimmer area, 18X24X9 for the return pump and 30X24X12 for a fuge/frag area. This should be about 75 gallons in operational volume and allow for about ~50 gallons in overflow when the return pump is off (I'll use a wye check valve on the return, but never trust them.)
All that needs to be added is a manifold and slight rerouting of the siphon and trickle drains to incorporate the occasional use of filter socks. I'll create a 5 tap manifold for the GFO, GAC and BioPellet reactors and a couple spares.
I think I've also changed my return pump selection, deciding to go with the Waveline 12000. It provides more flow and head pressure than the Diablo. The only inconvenience is the intake is larger (1.5") requiring some plumbing changes to the saltwater mixing station.
Still researching GFO, GAC and bio pellet reactors. I've had lots of flow issues with the BRS reactors over the years, so perhaps Vertex or NextReef MR1s. I'd like to use a manifold tap to drive the CaRx, but I've had such great luck with the Cole-Parmer - I'm not sure I want to fool with it.
I also decided on a Vertex Alpha 250 as it will run happily in 10" of water. Perhaps the greatest challenge will be fitting all the "Dry" equipment into the remaining 22X29 space in the cabinet.