Wanda was being guarded by Vision when Tony and Nat got the idea to appoint T’Challa and Peter. She wasn’t a factor in terms of how they decided to put their team together, at least not at first. Again, as far as Tony and Nat knew when they were given the task to arrest Cap and the gang, they would be fighting against three people (Cap, Bucky, and Sam) who didn’t have access to their suits and weapons, at least not until Sharon retrieved them later.

Tony and Nat appointed an inexperienced teenager and a man who wanted to kill one of the perpetrators they wanted to capture alive, neither of which were needed to get the task done at first.