RE: Cessna wants royalties if you build a model of their planes!
Please do a study of what has happened in the courts regarding trademarks, copyrights, intellectual property, and such. If such things are not aggressively-protected by the makers, then they have a chance to lose their rights. Cessna could lose the right to their own name and trademark, as could any other maker. The creation of licensing has removed exposure to such loss.
Yes, some fees and insurance requirements are needed...take a look at what's happened in product liability litigation. Companies have been held up for large amounts of money when they were in no way responsible for the outcome. It happens all the time. If somebody gets hurt, it's never their fault because they must be a victim, and the attorneys they hire just look for the deepest pockets. Let your name be on a model and you could wind up as defendant in a multi-million dollar lawsuit. You must somehow be responsible because you let your name/product be used.