Hi,
while I'd like it to be the opposite, i tend to think you cannot trust human being until they proved you can do so -> I'm against giving +2 to everybody by default.
I agree with Stefan and I wouldn't go for a too drastic change, let's first move to something like the approach described initially: 3*+1 or 1*+2can merge a patch. If it makes it easier to deploy it, then also make it 3 points however combined can merge a patch (meaning nobody can merge on its own, despite I think this may affect productivity having some patches merged).
Regards, Pau