I think LCY-JER with BA would do very well. A lot of Jersey locals are very very loyal to BA and there is a high proportion of Gold/Silver Exec card holders knocking around. And as we know... points mean prizes. This loyalty was VG's (and BD's on JER-LHR) biggest disadvantage.
LGW has remained strong over the past couple of years, even with the increase in a/c size from 735 to 734 (an extra 40ish seats per flight), and with BE upping rotations to 7 per day.
With many businessmen commuting several times a week to the City, there is in my opinion a potential to shift some of this business to LCY, even at the expense of an LGW rotation perhaps. Of course it all comes down to the bottom line, which I doubt any of us would be privy enough to comment meaningfully on.
Re potential other BACF routes: I don't think JER-EDI/GLA would have sustain a high enough load, but MAN perhaps would. When BACX/BACON operated JER-MAN it was rare to see a flight without a load in the high 40's even on those knackered old Dash 8-300s. However this would mean a break away from BACF's current business model (i.e. LCY routes only), and would mean treading on BE's toes somewhat. If only they would!!