My main hope is that the system models the series well, and that we don't end up with all the main characters being gods compared to any 'chargen' PC.
Belmonte, you have mentioned a classic problem in designing any game based upon a book or a movie, and I'm not at all certain that there is an easy answer.
1. If the game is designed such that book NPCs are gods, then there is the implied frustration of never being able to compete with them in anything. Players may not feel like the star of the series because there are always greater characters overshadowing their actions. In essence, you get a RPG where we get to play Dr. Watson as we assist Sherlock Holmes. Such fun.
2. If the game is designed such that book NPCs are not much better than the PCs, we often get the reverse effect. "Hey, we rolled up characters and defeated Sauron. What do you guys wanna do next time?" D&D had this crisis when they put stats (like hit points) in for gods of various mythos, and their only avenue of escape was to invent the avatar. "Well ... you didn't actually kill Zeus, but you killed his avatar."
Either way, some people will be upset by the design choice. I believe that the best action in general is to target the top NPCs at the maximum level that PCs would be expected to reach with the hopes that extended play would eventually allow someone to equal and tie Harry, if not actually beat him.
Or Amber, where it basically says no PC will ever compete with the Elders--in spite of the fact that this actually happened in the second series.
I believe you are referring to the "Merlin was a PC" discussion from
Shadow Knight? Of course, ADRP is also designed such that each individual GM can determine the attribute scale for the PCs and NPCs in the campaign, so whereas in Zelazny's world (for example) no one could out-Strength Gerard it is certainly possible for a PC to do so in someone's campaign if they so choose.
The wonderful thing about the ADRP character generation system is that all characters of equal point values are theoretically perfectly balanced. If some attribute or power seems to good a deal, it's probably not worth what you think it is...