I think I suggested the Rainbow challenge once, but I had some extra rules or something. Like you could start with any colour, but you have to go in order of colour from there on, so if you started with yellow, your second Pokemon would be green, and third would be blue etc. There would be added rules or something, like Pokemon such as Castform/Ditto would be wildcards, so they could replace any colour, or some optional rules, like your Pokemon must be able to learn Rain Dance/Sunny Day via level or something.
Like I said when you first posted this idea I love it and if you're not up to making the forum or participating right at the time of conception I'd love to make it a challenge in the Dream Theme since I need some harder challenges (my whole thread is beginning to sound like a loophole to get around the rules but I'm doing my best to complete them and making it an overall challenge by collecting badges and becoming competing champions).
Another idea I have borrowing from Chao's Chess format was a Law & Order type thing
Judge: Pokemon in this slot must be a duotype where the types are oppsite (ex. Water/Electric, Flying/Ground) Further more every move it knows from re moment a move needs to be forgotten, must be a different typing. This is because a judge is always impartial and must hear all sides.
Plaintiff: The Plaintiff is usually the victim in a criminal trial. Your Plaintiff didn't see the attack coming nor had the self defense skills to stop it. I figured the best Pokemon type for this slot would be a pure normal type. Also if this Pokemon faints you look at the type of Pokemon that defeated it. If you have any Pokemon in your team that are weak against that type they are boxed. Once one piece of the defense falls apart so must everything else. (Basically if your defendant let's say Wigglytuff gets killed by a water type all electric and grass types on your team are boxed) The judge, however, no matter what the typing is immune
Defendant: The Defendant is innocent til proven guilty, but let's face it they are probably up to something shady. In this slot you may use the shadiest Pokemon of all... If this type of Pokemon has ever been used by a Rocket, Aqua, Magma, Galactic, or Plasma GRUNT (not executive or boss) they may be used in this slot. However, if this is an evolvable Pokemon and it evolves prior to the Elite 4 your Defense Lawyer must be replaced with a new Defense that is at least 10 levels lower than your orginal. You made your defense fall apart with your fearful changing appearance. You may bring back any boxed Defense Lawyers after obtaining the 8th badge.
Defense Lawyer: You almost have to have no soul to protect that evil Pokemon you call a Defendant :0 Someone hard who doesn't listen to the prosecution at all. Must be a Rock or Steel type. Just like the Plaintiff if this Pokemon faints, depending on the typing of the opponent all Pokemon that are strong against that typing must be boxed.
Prosecution: Time to defend Justice and send those evil Pokemon back in their place. The Prosecution slot can never be occupied by a dark, flying, ghost, fire, or water type (we aren't representing evil nor destroying evidence). Furthermore the burden of proof falls on the Prosecution. By Burden in this challenge 3 out of 4 of your Pokemon's moves must be HMs that you shall not delete.
Jury: Now for the most important part. Unlike the judge the jury needs to choose a side to help sentence or free the Defendant. During the trial it's view on the case is always changing. The Pokemon in this slot must be a Pokemon that changes shape. Ditto, Cherrim, Castform... Or a Pokemon that can change its type or ability (Kcleon, anyone with Trace). When the jury faints the Pokemon representing the Plaintiff must be replaced with a Pokemon at least 10 levels lower than it.
This was the answer to my need to make a harder challenge. I'm still working out kinks and posted it here for feedback :x I think it has enough to stand alone in it's own forum but I wouldn't be able to participate right away.
I was also thinking of a rip-off/look a like theme for my forum where a team must consist of Pokemon that look eeriley similar to a Digimon/Yu-gi-oh/:0 other monsters from anime based on rhe slavery of fantasy creatures