Would it be possible to add a biome or biome tag restriction to the locations the portals spawn? As I'd like to make a portal to the abyss dimension spawn in ocean biomes specifically, as that makes the most sense.

Yes, this would be cool, especially considering the potential to have this mod work for more than just the Nether. (I've already created a rift that spawns in The End and teleports me to a mining dimension, but it would be nice if I could exclude the center island for instance).

Perhaps an implementation similar to how it's done with "biomeTags" in Better Mineshafts' variants file?

Really cool mod with awesome possibilities regardless. Thanks!