Disagree rocket man (re sparks) in the very nicest possible way unless you've got an alternator! (I know, Luddite tendency, little faith, old fart etc). Agree with all the plus points of the box of tricks - it's just the small problem of reliable long-term charging . . and roadside sparks maintenance. Agree with you 100% re 12v conversions though.
What do I know - but there are 4 people in the UK I think I'd send a mag to - SRM, Sean Hawker, Tony Cooper (v highly recommended indeed for quality and price by many v happy punters) and Dave Lindsley. Personally, I've recently had one complete K2FC from SRM, and two additional exchange armatures. Quite-to-very happy. In future, I'll go for the exchange guts and assemble-myself option, as armatures are not that bad price-wise and all the mechanical bits can be got, whereas complete rebuilds start to get a bit costly compared to the cost of the parts. Reasonable enough, skills don't come free. But while none of us has a Magmaster, obviously, if the coil has been wound and the pole pieces attached correctly, the rest should follow. If in doubt, cam rings are out there too.