It is quite probable, that if BA Balpa and the Scope plan is pressed too far, then GB (when the franchise expires) will decline to renew it (assuming BA does indeed offer a renewal). The present situation seems to be that every new route that GB would like to start gets refused by BA, because Balpa is leaning on BA management with scope threats.
BA will then find themselves with twenty routes being run by a new competitor called GB Airways in alliance with possibly another major airline. There will then be lots of cockpit jobs for BA pilots to fly B737/A320 on those routes, if BA has the resources to finance a dozen extra aircraft. The problem is that it has already been proved that BA cannot make money on these routes by themselves. It would be the road to further disress within BA mainline - twenty new loss-making routes, just to keep the pilots happy flying 'their own' routes in BA colours. They won't even have the slots, because the slots used are currently GB slots, won fair and square and built up over time. Remember that GB goes back to 1931, in its original form, and to 1989 in its present form at LGW.
So, for the militant pilots at BA, I suggest you think through your plan. Will it really provide you with more aircraft to fly, or are you going to cause even more finacial stress to BA, and ultimately destroy your own prospects.
GB may be small fry compared to big BA, but it is not so small (or weak) that it is going to go away.
The best plan for BA pilots would be to get on with making their own outfit successful, and leave their friends in GB alone.