Reference sub 38 yr old Sqn Ldrs leaving at their option point, rather than try to maintain a failing system, I can offer the following solutions to this problem:
a) Promote less Sqn Ldrs to Wg Cdrs, so the Sqn Ldrs who stay in at 38 do more time in Sqn Ldr posts. We already have far more Wg Cdrs than we need (about 1,200 I think?)
b) Look at all the jobs done by Sqn Ldrs and work out how many could be done by competent Flt Lts (probably about 80%+). Rank creep has been getting into the system for years!
c) Promote Flt Lt aircrew (all officers) to Sqn Ldr on the basis of time. The engineers virtually do this already - or they used to. About 90% of engineers used to make Sqn Ldr, all you had to do was look in the RAF list and find there were more Sqn Ldr engineers than Flt Lts, an inverted pyramid - I think it was a way of making up for their lack of flying pay, a retention/recruitment method?
It only took me a couple of minutes to come up with those solutions - who knows what I could achieve if I were a senior officer and given more time to think about it .........
In case you hadn't noticed some of the above was tongue in cheek - but not all of it.........