Si j'étais toi

Question

I recently came across this phrase in a conditional sentence while reading: "Si j'étais toi,...", but I can't find any grammatical reference to explain how the stressed pronoun can be used as a direct object after the verb instead of what sounds worse but looks grammatically correct: "Si je t'étais,..."  Is this allowed just for emphasis or allowed within certain clauses, and is it unique to the verb être?

Answer

Bonjour Timoty,
Here is another explanation of disjunctive pronouns.  While the explanation here is very good, sometimes another view gives another perspective:

forms 
Disjunctive pronouns (also known as tonic or stressed pronouns) refer to people whose names have already 
already been mentioned or whose identity is obvious from context. They are used in a variety of situations in 
French, most often in short answers without verbs, for emphasis, or for contrast with subject pronouns. Here are 
all the disjunctive pronouns: 
 
disjunctive pronouns
moi (I, me)	nous (we, us)
toi (you)	        vous (you)
lui (he, him)
elle (she, her)
soi (one)	eux (they, them; masc.)    elles (they, them; fem.)

uses  
after prepositions	 	C'est samedi soir:	 	
Tammy adore Tex. Elle ne peut pas vivre sans lui. Elle vit pour lui. Elle veut se marier avec lui.	 	
in short answers or exclamations when no verb is expressed	 	Corey: Qui sort avec Tammy?    Tex: Moi!

with ni. . . ni, ne. . . que
 Tex (à Tammy): Je n'aime que toi ma chérie.

in a compound subject or object	 	
Tammy: Tex et moi, nous aimons aller en boîte.	 
	
in simple agreements or disagreements when no verb is expressed
Joe-Bob: Moi aussi!  Corey: Pas moi! Fiona: Moi non plus!

for emphasis
Joe-Bob: Eux, ils s'amusent, mais vous, vous ne sortez jamais.	 
	
Dimanche matin:	 	
after c'est or ce sont	 	Corey: C'est moi le plus nul.

with -même, to mean'-self'	 	Tammy: Arrête de t'apitoyer sur toi-même!

in comparisons	 	Corey: Il n'y a personne qui soit plus pitoyable que moi!

I hope this helps somewhat.
Ron