XL CoreXY front end-caps  

Definitely not cosmetic.

I see them as safety attachments, guards to prevent dangling clothing/hair being entangled and drawn into the mechanism.  It would be potentially dangerous to run without them.

I'm not going to screw anything up by removing them and replacing them with parts that I print, correct?

That depends entirely on what you print ... but you may be relatively safe if you ensure at least as much coverage without any entangling shapes.

Cheerio,

RE: XL CoreXY front end-caps

Right, pardon my poorly phrased question.  I understand they guard pulleys and belts from entanglements.  What I am wanting to be sure of that if I remove them will I screw up the tension or alignment of the XY belts.  Sounds like I would not.  I'm considering modifying the front of them to become an attachment point for camera, etc.

RE:

Looking at the parts, the belt tensioner is connected to the front end cap, so I would say you  need to re-align and adjust the belt tension if you remove them.