Yes, and yes. To make the Champion's name fixed, when you edit the Trainer you simply need change the class to the other one called "Champion". iirc there are two, and one forces the loading of the rival's name while the other uses the name defined by the trainer's data. Making the Rival's name fixed throughout the game is pretty easy too. All you need to do use diegoisawesome's Intro editing tool and you can opt to make nicknaming the Rival disabled.
As for the fixed teams, you have two options. The first would be to edit the script for the champion so that the battle only uses one team instead of the three it does. The second would be to simply make all three teams for the champion the same, assuming you don't plan on editing the script already.
