One thing I will say is the transition between Frank and Charles was handled much, much better than Trapper and B.J.
Though, to be fair, Wayne Rogers didn't officially leave the show until their mid-season hiatus, so I can see how they had to haphazardly write Trapper out of the show by having Hawkeye miss his plane by ten minutes when he and Radar go to pick up B.J.
With Frank and Charles, on the other hand, bringing Charles in while there's a search for Frank, and eventually we see Potter and later Hawkeye and B.J. speak to Frank over the phone made it feel like it was at least still part of the story, if only in spirit (so to speak).
On a somewhat related note, there's a really funny blooper from Charles's first episode at the 2:16 mark of this reel: