I think you should add the ability to move down in weight
This has been discussed on here before a few times. I think the main argument against adding it has been the fact that it very seldom happens in real life. I think a good compromise would be to allow champions to move up and down between weights which they hold belts in (even if they could only hold one belt per weight class for purposes of advancing the game world).
We get asked this so frequently that we recently went away and checked the numbers for this in terms of fighters moving down weights and as importantly what happened after they went down weight. The problem for us in this is that to simulate it realistically it broadly speaking happens so infrequently it would be a very rare game feature. If you then look at the data and find that very small group of fighters doing this do so on average for one fight before moving back up again. The jury thus remains out as we would hate to spend time on something that is not going to happen very infrequently and then only temporarily…