After reading all of your great suggestions and doing some research off of them, I'm close to decided on the D500 + Tokina 10-17 FE as a start. I'm still looking at which housing but Bluewater is having a sale on the Aquatica housing for this camera (about $450.00 off) so that housing has now come in to the competition (along with Subal & Nauticam). We'll see what they all look like once ports and accessories are added.
There were a few questions above related to MFT cameras. I have been an Olympus MFT fan for a lot of years and the rig I'm replacing is based on an OM-D E-M5. This was a very fun and usable setup for me for several years of pictures. I'm fond enough of it that it has been hard to put it up for sale but it is time. :-) I also had an OM-D E-M1 mark II that I just sold. I didn't have an underwater housing for that one but it took great pictures on land for its smaller sensor (and fast shooting). I went through a personal camera audit and found that my go-to cameras now tend to be my Nikons (D810 and D500). I did consider the E-M1 as my possible new underwater camera but I just think the Nikons - even the cropped sensor D500 - just offer more (its sensor, though also cropped, is bigger than the E-M1/MFT). Again, this is not a criticism of Olympus (I love Olympus and will miss them now that they've abandoned camera manufacture). Their MFTs have been great, hardy little cameras. I'm just going in a different direction now that I think will serve me well as a next step.