If I were you I would buy the 12-50 port plus gear. This is a great all-around setup.
The 60mm is sort of an extreme lens, not for "everyday use".
When I started with uw-photography with a Motormarine camera I wanted to have a camera-lens combination for every situation I might encounter during a dive. So I carried with me two macro lenses and a wide angle wet lens. I ended up with not getting decent photos at all, because I was busy changing lenses and looking for small and big stuff at the same time, which is IMHO just counter-productive. As soon as I accepted that I might miss something due to the wrong lens and went down with macro OR w/a only, I relaxed and shot photos that were not as bad as before.
This said, I would not buy the dome port. Just my 2 cents...
yes, you are wrong: 43mm standard has less magnification than 43mm Macro - just check with your lens with the closest possible distance on land!
As it was written somwhere here in this endless the Nauticam zoom port is more versatile by itself. The discussion about alternative solutions came up because of the high price of this port. Alex Mustard uses this camera as his backup-system, so he did not want to spend that much on the port. With the Austrian zoom (100$ ?) gear you obviously can zoom, but you will loose the (high magnification) macro mode. If you already own a macro port and an adaptor like the Subsee (225$), you will just have to buy the flip diopter holder (220$) to get access to high magnification (or, if you are brave, carry it in your vest and screw it onto the port everytime you want to use it).
But if you start from the scratch it is, IMHO, more advisable to buy the Nauticam macro port, which is what I did and do not regret.
Since nobody seems to know, I just ordered two of these arms. They are compatible with ULCS arms! I paid only 7.50EUR per arm, in the US they are even cheaper (6.95$ at Adorama). A rare gem - an item for uw-photography that does not cost a fortune!