Well, don't get me started on cheap strategies... xD I really do have to say, I'm rather annoyed by the prevalence of cheapness in many people's teams. Can't wait for some fresh wind when OR/AS comes out...
Your idea is commendable, but it doesn't solve cheap gameplay issues. The general answer to attempts that try to balance things out by limiting will be: there's a way, so try and find it. I mean, there are so many cheap tactics, and priority mons is only one of many. They're not terribly prevalent I find (well, more than 2 on a team, that is), and if it's not priority it would be speed, or set up that would make things difficult for you.