I would have many different weight classes and many interim belts so that every fight became a "special championship event."
Also I would let old inactive boxers hold onto their belts for many years without even fighting in that weight class.

I would sell belts. When I ran out of belt ideas I would just buy another sanctioning body and work from several angles to get the unification fights I wanted.

I would appoint the worst judges and when they did a terrible job I would reward them with more top tier fights. Nepotism would be the only way I did things. A shitty job done by someone with mob ties or my cousin is much better than competency, because I decide who fights and wins anyway.

I would have a stable of known, albeit aging fighters, and I would round robin them throughout the years against each other so that we could all keep the money between us!