The easy soloution for BA:
The way it was done while I was instructing to get the hours required for my CV to be even read by an airline (just about the same as
JS's total now) and, I believe the way Low Costs want to do it:
1: Pilots paid by the hour for their duty (allowances) + flying equivilent to current salary at say 800 hours flown.
2: Pilots pay for all their check flights / sims.
3: Pilots pay for their own training.
4. Pilots pay for any recurrent / additional training needed.
5. Pilots pay for their own benefits ie health care.
6. Leave Pro rata on hours flown.
7. Seniority based on hours flown in the company.
This solves the problem completely. BA pays a high enough hourly rate so that at, say, 800 hours a year the pay remains the same take home as before. It is then entirely up to the pilot how much they wish to work. No one is disadvantaged by someone not working as much as they are.