(2) Assigning people RNGs they haven't already collected is another slightly less original idea.
(3) Trying to find your seed on the first attempt? (no set time limit; long-standing)
I have a few more ideas, but I'm thinking that most of these challenges would have to be made available for over four days, if not unlimited. Making a checklist of specific accomplishments seems more reasonable for RNGing, imo.
1) That is something we could do as another assignment/challenge thing... but it would be a different category. Honestly though, that sounds insane xD
2) Assigning RNGs? Hmm... honestly I don't want to assign people anything, but I want them to RNG what they want. I am worried that assigning might take away the fun.
3) Now this would only apply for 5th generation, right? You have to find your shifted frame first and all... not sure.
I was mainly thinking of challenges as you are thinking of assignments "RNG a Pokemon that is your least favorite!" or something. I'm not sure at all though.