I play it like this all the time, and I can say it multiplies the fun.
Stalemates are a lot less regular, and the creeps are actually dangerous; you need an dedicated anti-creep DG to kill the waves, and they can kill you quite easily if you don't waltz in. You can't just walk in kill the creeps and continue on the towers, you need your own creeps to defend you against the towers. All in all an improvement.
So set minions to hard default, but keep tower strenght like it is now.
