If you can build within the radius of *any* conyard, then you haven't solved the problem, since people with 5 conyards can still drop 5 buildings at once around a single conyard. (Having a conyard ~15 squares away from someone's base isn't so hard). 

The solution I prefer is to use a single queue for building construction. I think until we do this, we should disallow MCVs from being built. In gameplay, I haven't seen any negative impact of disallowing MCVs.