I know this may seem a bit confusing but first lets revisit your numbers. If you look at the current Nauticam port chart the 12-40 is listed with a 47mm 85-120 port extension and the Olympus 7-14 is listed with the 55mm 85-120 port extension plus a 10mm extension. That makes both within 2mm of each other at 67mm for the 12-40 and 65mm for the Olympus 7-14. I would expect either configuration to work with both lenses and the 180mm port.
For the ZEN 170mm port as you say the distance for the 12-40 is 60mm and the 7-14mm is 80mm for the port which is 170mm.
This is what you have not factored in, FIRST the Nauticam 180mm port glass sits in a port mount which has about 15mm of extension from the mount to the start of the glass while the ZEN 170mm port mount is about flush with the glass. This difference adds the additional extension for the Nauticam port. SECOND is that the distance from the point of lens to the spot where the virtual image begins is calculated for a zoom lens at its widest angle of view. So 7mm and 12mm. As the 12-40 lens extends to a greater length the dome begins to act more like a flat port as you get close to the glass. Since the 12-40 is about 84mms before being extended and the 7-14 is about 105mm and has internal focus rather that extending is needs to sit further from the port than does the 12-40mm. Because the Nauticam 180mm dome is wider the 12-40 can sit a bit further away from the glass than with the 170mm port. The extensions lengths are about the same but the ZEN port has a flat 120mm opening into the port while the Nauticam port has the same 120mm opening but then angles out preventing vignetteing with the overall longer port. If you look at the two photos you can see the ZEN 200 port on the extensions and the Nauticam 180mm port on extensions with the housing sitting on the tanks.
I don't know what source you are using to compare sensors but that is about as silly as saying that the FF Canon 5D IV sensor has not really progressed much over the 5D sensor or that the $2000.00 Nikon D500 has not progressed much over the $1000.00 D100. I have been shooting with the Sony A7R II for a year and a half now but regardless of image quality which is clearly high by any standard the Olympus system is still makes a better underwater system overall.
Apples to apples Mike, the D500/D750 announced at $1997 and the D810 at $3000 with the Canon 7D at $1800. The E-M1 announced at $1400. and the Olympus E-5 the then top "pro" camera announced in 2010 for $1700. Bitching about the price is quite common with many new camera releases. In the EU the E-M1 II with a select new pro lens like the new 12 to 100 F/4 Pro you get an £100.00 ($125.00) discount. A lot of people complained about the price increase of the E-M1 at $1400 over the E-M5 at $1000.00 and the fact (with E-M5) that you had to buy the camera with the 12-50 kit lens if you wanted to get an early release.
The E-M1 II has an excellent set of specs, better than D500 or 7D and most shooters buying the E-M1 II will be shooting the camera both above and below water with lenses like that wonderful 40-150/1.4 tele combo and be able to do it hand held because of the best IBIS in the market.
The bigger issue to me is simple, if I am buying a new U/W system all of the components for E-M1 system will be just as expensive as the components for the E-M1 II so I can have a system with the very latest improvements or a three year old version for a $600 difference if I bought the E-M1 new. The other option is that you can always wait another 3-3 1/2 for the E-M1 III which I am sure will be just as expensive or move to another manufacture like Panasonic GH-4 which cost $1700 at release.
For those of use who are already invested in an Olympus housing system and glass all that will be required is the new body and basic housing, my bet is that some used E-M1 housings and cameras will be coming to the Wetpixel market place soon.
I own the Sony 16-35mm zoom for my A7R II but I have been using the Canon 8-15mm Fisheye zoom with Metabones IV in a Nauticam housing. Ikelite has a solution as well using the eight inch port in believe. I would be sending Ikelite or your Ikelite dealer an e-mail for the part numbers.