Not so sure about losing points. Some members are away for some time because of work. Tom and Norbert for example may be away lengthy periods of time on film shoots. I may have misunderstood your point suggestion tho.
Hi, you're right, I thought about this already. The solution would be pausing an account, which is already possible I believe. A pilot could request a leave/sabbatical
for a limited amount of time. I think this should be done manually so pilots can't abuse this system. The pilot could just reactivate his/her account by filing a new flight report.
The general idea is that pilots who leave
without notice for a long time(some months) lose quite some point which automatically demotes them to lower ranks. If you're away for say 2 weeks you might have lost some points so you're worried about your rank or you dropped one rank down because your points were just on the edge. This would be the right kind of incentive to do some flying.
I know losing points feels a bit uncomfortable when you first encounter it but I noticed with other games that it really gets you hooked.
Losing points might also add balance when you introduce bonus points for missions/flights. Otherwise pilots might advance too fast.
I also think different wages(points) for various careers helps this system. A pilot who's been away for a long time without notice might choose to switch to Basic career because his/her rank is too low to fly an airliner. That's OK but his/her points add slower in this case so it also takes longer to regain the former rank. That would be fair, I think.