As you first stated only
one country needs to be below 40% for a win and a map change. So now, we don't have to worry about even touching the other?

This could make map winning a bit easy and obviously will change the current system.

Now, for example, the Bish could ignore the Knights who are putting up fierce defense, and attack the Rooks who are defending little to none. It has happened many times where a country has lost 60% of their bases to the other countries, as this can't be all too hard, specifically on small maps.