Isn't the danger here (for those who believe the premise is correct?) that pilots whose SEP Rating has lapsed could just go down to the local club once in a while and ask a duty instructor to supervise their solo flight and never actually revalidate their SEP rating - I'll get round to the test some day, just need more solo practice ...
It's seems bizarre to me that anyone would think, post-PPL, that they could expect to be sent solo without a valid Rating - I don't see it?!
You either have a valid SEP Rating or you don't - if you don't, you pass a LPC (or have the experience requirements) or you don't fly.
The idea of 'solo' is for a student pilot, pre-PPL, to gain the necessary experience to achieve the licence, not for a PPL to bypass the regulations.
You might just as well say when your ME/IR has lapsed that you'll just go off a do a couple of 'supervised' asymmetric ILS approaches solo at night in IMC for practice before your test!.