and just need a few people to debug/simplify the results. That adds a ton of planet locations (have a 'design San Fransisco' week) with little strain on the development team.
Unfortunately, designing missions using existing assets in non-iconic locations is easy to get CBS to approve. Letting random people design iconic locations seems like it'd be a harder sell.
Of course, if the players are building up your non-iconic content base, that frees up development time for the iconic stuff, so it might still benefit.