Pavel: did you make those measurements yourself? In my hands at least the flash durations are much shorter (measured via oscilloscope and pin photodiode). 23 ms seems to me way too long, more like 2.3 in my hands.
Well I mostly agree with two caveats. Like the OP I moved from 7D to EM-1 and now EM-1 mark II. There are a few differences. Firstly IQ is fine, I can make 16x20 prints with no issues and for macro the u4/3 macro lenses are awesome. Autofocus though is not quite as good as a 7DII with Canon lenses. A bit more hunting and a bit more time to get to focus, not terrible but not quite as fast either. The other issue is that in a DSLR the viewfinder is always on, with the u4/3 the electronic VF goes off then needs to be turned back on. a few other niggling issues with the Nauticam housing for the EM-1 ii, you have to take the tray off the camera to replace the battery (the battery life is better but still not as good as the 7DII). All that being said, I could shoot anything I really want and am shooting the em-1 ii; as a tool it allows me to shoot almost anything I want.
In a pinch (not all wine pumps will work, some are too big but you can often use the "cork" to fit over the bulkhead fitting) you can just use your mouth to suck the air out of the housing. Works fine.
Adam: While that is true in theory, i had a couple of Wiebetech enclosures die and no other array could read the drives. Maybe if they are from the same manufacturer with the same firmware it might work.