...this thread has done so much for the question at hand.
Assuming the amnesiac Magus is not Guile, then it's completely plausible for Dalton and Magus to have joined forces, but if Guile is the amnesiac Magus, then I'd hardly expect him to have helped Dalton with the fall of Guardia. I mean, Guile is completely lax and no one seems to know anything about the bloke. If he played a very strong hand in bringing down Guardia, someone would have to know--anyone--and he wouldn't just slip away willy-nilly; he'd be pursued, followed, praised: something would happen. I simply cannot believe that Guile would ruin a kingdom and just wander off like a mindless child.
Even if we examine Magus's role in the Mystic War, we clearly see that although he played a prominent (and possibly unseen) role, he had desires that he wanted fulfilled; and Guile/amnesiac Magus would still have to have some cause or desire and the fall of Guardia would either be a means to achieve that cause or the effect of his cause. Guile/amnesiac Magus, even as much as he likes to seek adventure, just couldn't have been a key figure in the Fall and vanish as if nothing happened...it's just too unlikely for him to escape unscathed, unknown, and unseen.
Now, if amnesiac Magus is not Guile, then it's completely possible for him to have played some role, but fuck if I know what it is...
