I believe Microtrains are considering a NEM version of their coupling, though as far as I'm aware they have not committed to producing one. At the moment these can be fitted to the older Farish pockets but not the newer NEM version, so they can't be used as a universal coupling.
I've recently fitted some Red Caboose couplings within rakes. These can't be separated without lifting one vehicle off the track, but are a fairly easy way of bringing the wagons closer together, making them a bit less visually obtrusive and (I hope) reducing the tendency to uncouple randomly. They are only available in non-NEM versions but Dapol do something similar for NEM pockets. At present I'm sticking with Rapido for locos and ends of rakes until the situation on Microtrains becomes a bit clearer.
I've also wondered about the Fleischmann profi-coupling (available for both pocket types I think) but a bit put off by the lack of available info on the Net and the fact that they can't be operated magnetically.
Looking at the magnetic intermediate couplings on the Dapol Voyager, I wonder if something similar could be used at the end of multiple units? It would need a north and south pole alongside each other so as to be reversible, and to be a bit smaller than Dapol's version. My idea is that the magnets would be strong enough to keep the units together in normal operation but using DCC or isolating sections one unit could simply be driven away from the other one. However this might also cause them to separate if one unit briefly lost power, so you'd need very good wheel-rail contact for this to be workable.