Since the Nether is getting an update that'll make it possible to survive there, even if you start there with nothing, more mobs should spawn in the new biomes, as well as have conflicts with each other (such as between Piglins and their zombie counterpart).
Mod that makes it so Magma Cubes can't hit you twice but instead will set you on fire
New magma cube variation - example being Ashen Cubes, same as Magma but has a gray outer body (minus their eyes) that take away your oxygen when they hit you, but are weaker than Magma Cubes (also cosmetic ash snow in the Basalt Detlas)
Wither Skeletons actually patrolling the Nether fortress + rare mini-boss Wither Skeleton always in full Netherite that defends the Blaze spawners backed up by regular sword skeletons in full iron
Wither Skeletons in the Soul Sand Valley that always spawn with Soul Speed 1 boots (lower chance for regular skeletons)
Piglins should be hostile to all mobs that can wear armor when said mob is not wearing gold or not holding gold (except Wither Skeletons, Piglins should be afraid of them, or a mob with a Soul Fire torch/lantern in it's off hand)
Also a way to zombifiy Piglins without taking them to the Overworld if there isn't already a method of doing that.
Oh and big Wither Skeleton Horses
