Kabam. Don't waste the Time and money you put into current war map
You have already invested time and money into developing this war map. Why waste it? Just change it to a three star only map. First of all, I think it would be fun and totally skill-based since most of us have a ton of three stars that are essentially just wasted. As rewards you could give some three star and four-star shards, alliance revives and potions. This would fit right in with, as you say, four and five stars will become more available.
But mostly I think it would just be fun and pretty much everyone would be able to compete at an "Equal" level since it won't necessarily be about, "do I have the right champ for this fight", it would be, "do I have the skill"?