Hi, I just released a small blueprint project focused on creating an aiming system for 2.5D SideScroller games.

It's currently a work-in-progress since the aiming animations for the character have not yet been added. But you can use it to calculate mouse cursor locations on the player's movement plane (without using an invisible plane). So if anyone's interested in using that feature in your games, you can get the project from GitHub:
https://github.com/RohitKotiveetil/U...5DAimingSystem. [The ReadMe section has some notes on how to get started]

And here's a short preview of the aim point calculations (checked against a top-down camera to verify alignment):