If Charles was there at the same time as Frank, how d'you think they'd react to each other?
Personally, I think they'd be initially united against Hawkeye and BJ's antics, but then Charles would be incensed by Frank's performance in the operating room, forming a three-way rivalry, before Charles would eventually become friends with Hawkeye and BJ as he does anyway, maybe a little sooner.
What do you think folks?