I like tying the number of troops to ENY much better than your first idea. But regardless, I don't see how this will stop the pointless ganging on a country that is already down and out.
Speaking of making ENY more meaningful, there was an idea way back when the arenas were first split to use ENY as a TRUE side balancer . . . if a side is under ENY restrictions, do not let anyone enter that arena for that side. Give them a pop-up that says "Your country is under ENY restriction of XX. Would you like to a) Enter the arena under a different country or b) try another arena." Have it kick in at whatever minimum ENY level - 10, 15, whatever.