When adding fights to an event and trying to use the Assistant for matchmaking (e.g. to find potential Main Events) the calculation can take quite a substantial amount of time with a large roster.
Adding the ability to cancel the process would save a lot of time, especially when one of the early results is the one you already want to pick.
Alternatively, have the default view on a specific weight class like it's the case on many other menus, as opposed to "All Weight classes"