"couldn't the "whom" be seen as the object of the infinitive and what
follows as a relative clause with an elided pronoun? "

Simply put, no. "Become" in the sense of "turn into" is intransitive and 
cannot accept a noun-phrase complement.

"Return without delay to become you truly are the person" is of course 
awful. The bare clause "you truly are the person" cannot be a complement 
of "become". A better paraphrase gives the infinitive a noun-phrase 
subj. compl. ("the person") followed by a rel clause which modifies "the 
person":

"Return without delay to become the person (who) you truly are."
-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Johanna Rubba   Associate Professor, Linguistics
English Department, California Polytechnic State University
One Grand Avenue  • San Luis Obispo, CA 93407
Tel. (805)-756-2184  •  Fax: (805)-756-6374 • Dept. Phone.  756-2596
• E-mail: [log in to unmask] •      Home page: 
http://www.cla.calpoly.edu/~jrubba
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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