Point 1 - is there a similar decline in PPL issues?
Not at all.
Point 2 - how many high income people have emigrated since 2002 - many thousands
Many, though I doubt this affects GA very much; for the % of the general population is still very small.
Also I don't think many high income people (say, £100k+) have been hanging around GA in recent decades. The high income men driving nice cars have moved on to more interesting activities (more excitement, more interesting females around, or both) back in the 1970s, as far as I can tell.
Removing the need for a CPL from the FI rating only currently applies to LAPL training
Where have you read this, bose x? It's categorically not what the #1 man in charge told me personally earlier this year.
Anyway, whatever is happening is specific to the IMCR, and it is a
strong effect. I don't think it is the clapped out planes; they were just as clapped out when I started my PPL in 2000. It is a major attitude change somewhere. Are schools not advertising it? That would be a key factor because AFAICS most people that do it do it quite early on in their flying career, before they have got clued up on the real world out there.
There is a drift towards permit types, quite a strong one, but that just means the pilots are flying IMC enroute if necessary.
Once you learnt to fly instruments, and you have a decent GPS, you won't be afraid of IMC. What makes the IMCR (and the IR) hard is a) the lack of situational awareness without a moving map and b) the need to perform complex tricks like NDB holds.