Interesting post. I originally did an NPPL SEP 7 years ago on the PA38. A house move prompted me to check out and then buy a share in an Icarus C42 at a nearby airfield. Fab little plane in every sense and at £42 per hour!
Upgraded to JAR PPL last year, but swapped my share to the Eurostar (can still fly the club C42s if I wish). I have the 100 hours P1 and the 60 microlight hours required and I'm seriously thinking about doing the Microlight instructors course this summer.
But, not with a view to a career change. Will be a part time/weekend job if I do it.
In terms of money, my club has a few full time instructors. I don't know what they are paid but it's not fortunes.
I can understand why the hours rules are as they are. They were written when a microlight was typically a homebuilt scaffold pole/tent affair with a screaming 2 stroke bolted to it that floated about at 50kt. It is an utter nonsense that hours in a C42/Eurostar don't 'count' when they do Group A versions of the very same areoplane. As has been said, they climb at 1000ft/min and cruise at 80-90 kt. Compare that to a C152! And burning 14L Mogas per hour to boot!
There is a trickle of people from GA attracted to the new generation of microlights. I think this summer of tightening wallets will be very telling.