This is great, thanks for inviting us to participate in this session vicariously. What a lucky subbie you have!!!
Some ideas, control could be "testing" subbie to see if he will resist torture, and if so control rewards subbie with a nice sensual session, including his preferred activities, conversely, breaking under interrogation could result in punishment.
Control could instruct subbie that he must go undercover, and either be feminized by one of the mistresses (who acts a bit like Q from James Bond) and then purchase a specific item at an adult store in full feminine regalia that will be the signal for the next contact to bring him to the next location, or even meet someone specific at a drag friendly place. A mistress sponsored by control could even shuttle subbie to the various locations in this mission, a bit like Moneypenny.
Having control assign a Domme partner to help him from mission to mission, and "break him out" of some scenarios could also accomplish your goal of transportation and safety. In a twist at the end, said domme might even change teams and betray the subbie to the evil domme In the penultimate session. I am sure a few subbies would volunteer for this duty as well...schedule permitting, I certainly would!!! Good luck, this sounds like it will be a wonderful session, mostly due to the creativity and preparation you are putting into this, he is a very lucky subbie indeed!!!!