They should have let you customize each companion the way you wanted to. Maybe I want to give Tanno an Assault Cannon.... Nope, all he can use is this funny stick.
The only limit I would have placed is Force users vs. non.
This is an excellent suggestion. I don't want to be forced to use certain companions because of their pre-determined roles - e.g. my light side operative is stuck with Kaliyo and Scorpio as the only tanks, and they're both a psychotic as they come. Would be awesome if you could have 'kits' which allow you to change their roles.