I would suggest that making better assets with better origin points/pivots and accurate angles is the best practice solution here.
Then again - you are correct that this is not “natural”.
But you have to realize that Fortnite isn’t natural. Its block based and only slightly better than the block mojang game I can’t remeber the name of.
This whole engine is essentially just a Fortnite Simulator - you cant really expect things to be better…
Therefore…
Make your levels with a base object that “hosts” all other items via parenting, then rotate that custom object to taste.
The level loading can stay in the Block/Grid orientation. The main piece inside the level can be used to provide that extra manual tweak which will make things look more natural - hopefully.
And if you set your mesh actors to movable, you can probably also rotate the piece at runtime with any rotator component, timeline, or really any other way you can think of to affect rotations…