What might work is to block off the pop door inside (where the ramp is) with chicken wire and then so no one can get up there and then add a roost in the lower half. That way a couple chickens would be forced to sleep down there. The other two can jump up into the main coop through the side...
My idea was to take out the side on the end (opposite the coop), add some more run, and build another coop on the other end…but then you might as well just build a new coop, right?