BMI do not have an aircraft capable of landing in GCI as far as i'm aware so that would rule out any JER/GCI rotation ex LHR.
I would also suspect that in order to get the high yield traffic they want then they'd have to sustain any LHRJER route with either A319/320 capacity providing some form of premium service. Correct me if i'm wrong, but i'm not sure if either A319/A320 are certified for GCI?