If you look at the design for the BMW pannier mounts I can't believe it would be that difficult to copy the fixings and then mount them on the pannier of your choice. In fact - calling Mr Cymarc! I'm sure there would be enough of a market to make them commercially viable!
I've posted a couple of pics of my panniers below with the OEM fixing. It is cut from a single piece of metal and then the four little lugs have been welded on. Not a significant engineering job! Admittedly, the bracket bends at each end to match the shape of the OEM panniers but you wouldn't need this if you were going to fabricate something up to fit another pannier make.
If you regularly carry lots of stuff around like computers, gym kit, weekend clothes, tools etc. hard luggage is IMHO king. I don't think that Vern still makes his Worldbeater panniers which are brilliant. When mine die I'm likely to buy Jesse luggage from the USA but that is inferior in terms of finish as it's powder coated rather than anodised.