Well this benefits/problems discussion tends to lock threads.
I am sure people can think of benefits (users and devs). I am sure people can think of potential issues (I've seen all that were presented in the past easily answered but anyway).
Personally I think UME should be MAME. That's it, as simple as that. If there are benefits more than problems (or benefits without real problems), then... why not.
But let's not open this discussion just yet (with the above I just "recapped" a bit of what has been said in older threads). Let's let the dust of this whole thing settle. We'll see how it goes.