I have an LTD H-1001 , 12's and i keep guitar in C# standard or drop B . I want to play some standard tuning stuff from time to time and since i don't have 2 guitars , I was wondering would it be possible to put a capo on 3rd fret while in c# standard and make it an E standard that way? Would that be possible sound wise and would that hurt the neck in any way since its 12's on the guitar?
It's ok with me.

Won't hurt a thing.
“Ignorance more frequently begets confidence than does knowledge.”
Charles Darwin
Nothing wrong with that at all, provided the songs don't need what would have been the highest three frets of your guitar.