It would be even more challenging because it plays only on chance. But the problem is that people could cheat by choosing the specific categories to mix and not making the run completely random. So what are your views on it ? It could be a category extension.
(sorry I don't speak english)
There are a solution that I propose in discord, but only for 2 modes combinations. Go into the discord and in the chat of modes requests (I dont remember the correct name) and go in the fixed messages... you will see my message, and if you liked, pls request to be add too (citing my solution), because we will have more chance to become this category real!
If you really want this to become real, create a spreadsheet where people can post runs. If some blender categories get added to speedrun.com, people will want more to be added. Even just two mode combinations will result is 66 more categories.
have people show they made it random in the run
I made a spreadsheet to put in perspective how big this would be https://docs.google.com/spreadsheets/d/1SXr4T2NYIIg8ZL9Xy-2nClnZMhNeWB56wl5Y-pKfnfA/edit#gid=0 there are almost 6,000 combos, and i didnt even include blends of 4
My suggestion is to just have it be entirely random, the only variable being how many gamemodes are combined in the run. This is a CE after all, right?
that or the mixer mode could be it's own board, but it will be very hard to convince the site mods to do that.