Not sure if you take suggestions here, but I had an Idea that seems like it would fit this mod pretty well and thought I might as well add it here rather than post it as a massive block in the comments on CurseForge.

This would add a parallel world dimension that is identical to the overworld, but slightly wrong. This dimension could be accessed by various uncommon, inconspicuous gateways scattered around the world, such as lone stone arches, fairy circles, doorways in a ruin, torii gates, etc. Appearing as mundane structures or blending into the environment so that players don't immediately realize that they've traveled to another dimension (could also have a chance for the portal not to spawn in some structures so that there's still some element of uncertainty) to give a sense of unease/intrigue as they realize something's weird. The parallel dimension would appear as normal, but something would be different than the normal overworld; from more subtle differences like player placed blocks and known mobs not being there to more obvious things like structures being shifted around, biome colors being off, or even being entirely mirrored across an axis.

This would be a world generation option similar to dimension stacking, allowing the player to go in completely blind, fine-tune the properties of the parallel dimension, whether or not the Nether and End also have parallel dimensions, or just disable it completely (possibly even being able to add multiple parallel dimensions per dimension).

There should be one for all the dimensions, including dimensions added by other mods

It could be in another mod.

How so? The idea is fundamentally based on the seamlessness of immersive portals and the pre-existing features of dimension stacking, and world wrap. Sure, having random portals that lead to another near-identical dimension could be done in another mod, but it would be pointless without the seamless transition keeping the transition ambiguous.

I think they meant another mod that uses Immersive Portals as a dependency. It seems a bit outside the scope of the base mod.

I would make this if i could.