I love the mod and my kids love it far more than I do, but it makes survival mode rather trivial. I kill a bat, and I'm basically invincible. It gets much worse with Biome O'Plenty and nether wasps, which have player-level health and armor still seems to be factored in.

It would be really nice if there was a way, either through console, config, or ideally through crafting, to limit morphing to a specific area. I want to fly around as a bat while I'm building something, but it ruins the whole sense of exploration.

A kind of powered morph block that emits morphing power, or a morphing medallion that has a limited charge that makes it so I can't just fly around for hours without any drawbacks would make your mod very compatible (from a gameplay perspective) with vanilla minecraft.
Perhaps also limiting morphs by a time before you forcibly morph back would also accomplish the same thing. Again, I'd like this as an option, not as the default behavior, just so I can still have a survival mode feel AND be able to morph into stuff.

Sorry, I don't really have time or motivation to work on game aspect of Metamorph.