7. Captain Rex
Another fan-favorite character from the Star Wars: The Clone Wars animated series, Captain Rex was one of the few friends Ahsoka had left following Order 66 and would be a great inclusion to her series.
The two escaped the Republic/Empire together following the end of the Clone Wars, with Rex aiding Ahsoka to fend off the Clone troopers from executing her, after which, the two went on to aid efforts in the Rebellion.
Canonically, Rex was last seen as a part of the Battle of Endor, on the ground as a part of the Rebel troops with Han Solo and General Leia’s assault on the shield reactor on the Forest Moon.
The Mandalorian timeline is set five years following the battle, so it is perfectly possible that Rex is still alive and could reasonably reunite with Ahsoka for the first time in live-action form.
Adding onto that, Rex is a clone of the Jango Fett template, a character portrayed by actor Temuera Morrison. Morrison himself recently returned to the franchise, portraying another clone of Jango, Boba Fett, and is set to star in his own spinoff as the character.
Having the actor returning to Star Wars and the character Rex still being alive following Endor all points to it being possible, and maybe even probable, that Captain Rex will show up in the Ahsoka series.