Well the North Terminal is to the North of the SouthTerminal so seems OK I think.
Virgin don't want to have to move the
Clubhouse as it would be rather pricey. There is/was an exisiting strategy to get the long haul carriers into the North Terminal to make use of all the space BA no longer use. Continental and NWA both moved across following Thomsonfly to join First Choice, leaving Virgin and USAirways. I think they stopped this after both CO and NW left soon after their moves....
It's a bit of a mish mash but not unworkable.
This could also help Gatwick to improve its appeal to fussy Business pax as they would not have to worry about sharing a terminal with horrible, evil holidaymakers!!
Remember BA Gatwick focusses on holidaymakers.