In case there is an unexpected christmas: This is also on my wishlist. The prefixing makes the additional waypoints relatively useless, the not standarzised prefixes make the additional waypoints completely useless.
I think the two-letter-code should be fixed by waypoint type (when multiples are required that is a problem, I know). The path choosen now means, we can never have anything new, which requires a new two-letter-code, because by saying "anything not used yet is allowed" means now all codes are blocked.
Additionally this means, that the waypoint name gives no hint about what this waypoint is, which I think is a disadvantage (if I prefix my parking coordinates with "th" and my trailhead coordinates with "pa" that only increases the confusion).
I think the additional waypoints are a really nice idea, but not implemented all too well. But with some changes this can become a powerful feature.
Nils