As you'll read, they are suggested by the community and I review. As we're trying to spotlight one a week, your suggestion may be more difficult to implement. However! I'm open to feedback so feel free to leave it here
User Generated Content is all about adding a level of customization to the game, allowing players to create content that they and those of similar playstyle will enjoy. Some love a great deep story. Others prefer interesting mechanics and gimmicks pushing the boundaries of the engine and tool. Another group just loves to blow stuff up with as little in the way of that as possible. But it is about the customization and diversity that can be added to a game that makes UGC amazing. When you limit that artificially without a good reason that will stifle the appeal that the UGC brings. It is one thing to say something is exploitative and I agree the grinders are. But a well designed combat encounter is a well designed combat encounter.
Taking that to the next step, the Spotlight is simple. The spotlight is about showcasing the best of the best created with the foundry. Not the best story. Not the best combat. But simply the best. To that end it should include a large variety of mission types and styles. If you are trying to appeal to a wide audience one should cast a large net. Unless of course the goal is to only attract a select type of player or playstyle to the foundry and UGC in general.
Going even further, the best selling PC game of 2012 had it's development team heavily criticized for defining 'fun' for the players. They are currently doing their best to change that perspective and have agreed that it is up to the player themselves to determine individual what is fun and for them to try and accommodate that. Battleship Royal Rumble has already been determined to be fun by a large number of players. It is not exploitative in the least. Do not cater to special interests or a narrow definition of what should be done with a creative tool nor what should be promoted with it.