I spent so much time to replicate my favourite platformer SuperMarioWorld (about a month prototyping) and came without a solution mainly for these two:
Creating a pawn with a square collision box makes some weird collision behaviour with the ground sometimes, And it is required to make a movement system from scratch.
One way collision platforms, a common element for 2d platforms is currently impossible for multiple actors interacting with it. (as some levels in super mario world feature multiple jumping enemies that spawn under some platforms and jump over it, not efficient to make a new collision channel for each turtle)
Unreal is clearly not perfected to tiled 2d games, but it is in progress i believe.
If an update come out OR someone manage to make a decent workaround please share you information here. (or if i am simply missing something obvious)
I am going to proceed to next 2d project in mind that does not have that limitation, for a while.