The 50 thing is a choice events team members make, they can do however many people they want in an event. And the see-through avatars of other players helps reduce lag and allows you to see yourself quite easily. Saying something unique or in caps could also help you see yourself. Also, if it's less than 50 some people will complain that they couldn't get inside.
The TTS and Spar Tournament idea: people would complain about not being able to use their weapon that they bought.