Interesting times indeed!
A few facts.
Comparing the salary and terms with flt crew will get you nowhere
BA would have already worked out that any strike would be illegal, therefore this will not happen as it will bankrupt BASSA.
The lack of effort toward LGW SF a few yrs back will seal the fate of LHR
BA loved the lack of unity between bases, see previous point
Ex GLA base, ex call centre staff, etc as mentioned. No relevance on seniority as BA will do what they like as its a 'volunteer' new fleet.
There will be more than enough new people who will go for the fleet.
Enjoy the prem trips while you can! Hkg,JNb etc will become min rest under national CAA law, not BASSA's rules
Finally, I dont want this to happen either, but ignoring the facts and talking about other groups T and C's will just speed up the process and be a gift to BA. It may not happen, but get your head out of the sand and take a practical approach and be prepared in advance.