D&D 5E Have players play their own rescuers

It is usually fun to play another PC once in a while. A bad(ish) character setting up a prison break and attacking guards and such would be fine for a session or two. This leaves open several ideas for further play. The PCs can now go with the other group. The can be hunted by the law or working to clear their name. The law can later hire them to go after the other group if they manage to clear their names. They can owe a favor when they become rich or gain the knowledge of a powerful artifact. One of the other group can join the PCs on a quest or become a henchman and turn from his former life.

When I give the players a NPC to run for a while I usually have a monster stat block format for the character. It lists the basics that the player will need like armor and HP, but lacks how many torches he has and hair color. I usually do not make NPC to be classed monsters, but only similar. I do not have a fighter NPC, but I have a guard or warrior. This way I can give him a cool power or not give every fighter power and it still works. Fighter-types usually still get 2nd wind and crit on 19/20 though. The may get only one save instead of two and only one or two skills I think are good to fit in.

I just wanted to thank everyone for their input. I ran this today and it went so well that the players have indicated that they want to occasionally go back to these characters and fight for the resistance!