Unfortunately, some of my ideas are rather simple in nature. What I'd really like a mod similar to Orespawn that allows YOU the player to distribute vanilla ore and modded ore the way you want not the way the game wants. SO it could either be made difficult to find anything or rather easy to find anything. I'd rather this mod be made for both fabric/forge (unless it has already been done for forge)/Quilt. I miss that about 1.12.2 the most.
Well that and mystcraft. But I'd like something similar to mystcraft but for fabric/quilt. This might be too much to ask at this point, but maybe just maybe...It can be done in a balanced way. But instead of books it can be done using scrolls or parchment made from sugarcane or bamboo. Maybe the glyphs (similar to symbols) you get can be put into a printing press and it can be saved into a book of some kind or parchment. So that you can use a pen and copy the glyphs into the scroll for you to use to get a new custom dimension you created yourself from the glyphs saved. The scrolls can be put on Scroll stands similar to waystones, but you'll need a scroll or parchment to take you back to the world you just came from so you aren't trapped there. or maybe you'll run into a place so far down that it will go into the void for you to teleport back to your world. However, you will also run into worlds with certain negative effects and it will affect you by either making you stronger, weaker or slowly kill you unless you can find ways to negate those effects, along with blocks that will shatter and corrupt other blocks around them shattering them as well causing the world you created to slowly delete itself and turn into a void world unless you can find a way to heal the shattered blocks.
I'm not saying that you should copy it, but make it have a similar feel to it or make it completely unfamilar. I don't mind either way.
As I said earlier though, it might be too much at this point. Hopefully the ideas I've given you guys will help in someway.