I have a poly with many subelements and I can’t adjust the pivot point correctly because of it (specificaly, I can’t reflect pivot, it reflects the object also). What I want is a single poly with only one element. I know how to detach and attach elements, I know how to weld vertices, but none of this gets me to the solution. 
If I understand you correctly… You have polygon mesh with multiple attached meshes and you want to adjust the pivot point precisely!
In the Hiearchy Panel > Select (Don’t Effect Children) and adjust the pivot point.
Hope this helps!
sw00000p
Nope. It deselects the Affect Pivot Only.