There aren’t many (ceremonial) Colonels/Commanders in Chief (is that the right term, depending on unit?) who are not senior, working Royals
There’s the King of Norway and of Nepal, and the Duke of Wellington. Any others?
I don’t think a non-resident non-working Royal is a terribly good choice for this role.
There will have to be a reorganisation to deal with the departure of Prince Andrew, but perhaps that’ll have to wait until after the Sussex review (though I bet planning is already underway, with various options depending on his plans mature)