If you want to dump US, your main choice is DL in terms of a primary carrier. Of course, flying US or DL metal you can go a couple different directions with FF miles...

UA's program is huge and the airline is too darned big to go totally Chapter 7. Therefore, you could continue to fly US with its strong timetable at CHS and accrue UA miles.

I don't know whether UA will comp you a status or not, but since you know the counter/gate people at CHS, you might get courteous and respectful treatment (thanks to your Chairman's status) even as you are building UA miles/status.

Just curious: what makes you think US is about to disappear?