<<I know this is digressing but what is the difference between LAMP (where a lot of work is discretionary) and a mfg-specific scheme where the MO ticks all the boxes but doesn't do some of the work?>>
Well I guess it boils down to liability in the event of an incident.
Using LAMP the engineer has lots of 'wriggle room' as he/she is required to use experience and knowledge to judge where and in what depth to conduct maintenance. So could not be expected to know about some peculiarity of an exotic foreign aircraft.
Manufacturers programs however remove all doubt, as they say what has to be done and when to do it, and cross refer to the manuals that say how to do it. So accident investigators or insurers can go through the program and see clearly if anything has been missed.