The sentence with "soyez" is not correct. As you guessed it, the author meant "you are all what I thought you will/would become".
For a better understanding, the sentence may be replaced by the following:
Vous êtes celui que je pensais que vous deviendriez.
The use of the "conditionnel" (not the subjonctive) for the final verb "seriez" is correct. However, the original formulation (with soyez) or the modified one (with seriez) are so far-fetched that I don't imagine most French speakers using them.
As mentionned in @AlexandreP.Levasseur comment, the author may have meant:
Vous êtes tout ce que je pensais que vous étiez.
What can be translated to "You are all what I thought you were".
To answer to Alexandre, both sentences with "etiez" or "seriez" are not shocking: I just think that almost none native speaker will use such formulations to convey the idea.
To translate "You are everything I thought you would be", on pourrait dire:
Vous êtes [vraiment] tel que je l'imaginais.