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I like the idea of battlefields but am not a huge fan of enhancements for them. I also think you could have regular enhancements that allow you to put a battlefield in play compared to simply starting with them. I'm thinking they could actually be fortress that say place in field of battle in the identifier.
We added the Territory Class enhancement in TxP only 3 or so sets ago so it hasn't been 9 years. Still I dare say that battlefields would be amazing.