I have posted my concerns about this as well and feel it still needs refinement. One issue is that FIA counts as enemies, this in theory is fine, the issue is that FIA can often get stuck in odd positions. A good example is the St. Pierre Coastal point. FIA can get stuck in the water or under the map and this prevents the point from being able to be built on.
"Enemy in the area" does work both ways, one tactic that the defenders use now is to often check build privilege as a sort of radar to know if someone is hiding or nearby. I really don't think this mechanic is all that much better than the previous solutions and both present their own issues.