I respect your opinion and I'm sure the nauticam em1 is a great setup.
But, you seem to imply that the epl1 does not have manual controls. I'm not sure if that's what you were trying to say, but just wanted to make it clear that all EPLx cameras have a manual setting and manual control of everything. Now, those cameras don't have as many dials and controls as an em1 or an em5, so you might have to go to menus or such, but it can be done. On my EPL2 in M mode, I find it quite easy to change the shutter or fstop. Just one push of a button, then the up/down controls shutter and the left right control aperture. All EPLx cameras I have tried work this way.
Also, all olympus housing give you access to all buttons on a given camera. You may prefer the ergonomics of one housing over another, but wanted to point out that all the controls are available.
The extension ring is the same part used with the Olympus 43 series housings (E-300, E-330, E-400/410 %20 Ect.) for use with the 1.4X teleconverter. The extender could be used to add the TC to the 50mm macro lens or to extend the 8mm fisheye. These parts are also sold by Inon, Athena and more. The dome is the same 170mm optical glass port used with the Old 43 Olympus 7-14 and a longer extension. The only new part is the gear.