Ahh, yes, spend more and more on gear that I use maybe once..... I know the feeling!
I'll have to leave it to Alex on the 60mm lens in the 85 port. He's the Nauticam Man.
On your and Mark's (AussieByron) comments on magnifying viewfinder, I totally agree. I bought a 45-degree viewfinder for my Subal D300 system about 10 years ago and, gotta say, it's probably the best and truest "investment" i have made in my system. It makes a huge difference for macro - even WA - work. In addition to providing a larger, image for focusing and composing (and, yeah, the aid to Aging Eyes), it allows you to get the camera to a lower angle for shooting upwards rather than risk smashing down into the coral or seabed. They are horrendously priced but, for once in my view, really worth the money. Mine has slowly migrated over the years from the D300 housing to a D800 housing and now to the D500. Easy to remove and install, solidly built, it has been one of my wisest purchases (ok, there haven't been too many of those).
The magnifying viewfinder and the vacuum valve system are my top recommendations.