Need the Eshet Yefat Toar be objectively, or even subjectively, beautiful?

Summary: Not on the level of derash, or even on the level of peshat. But to what degree?

Post: At the beginning of parashat Ki Teitzei:

11. and you see among the captives a beautiful woman and you desire her, you may take [her] for yourself as a wife.

יא. וְרָאִיתָ בַּשִּׁבְיָה אֵשֶׁת יְפַת תֹּאַר וְחָשַׁקְתָּ בָהּ וְלָקַחְתָּ לְךָ לְאִשָּׁה:

Must she truly be stunningly beautiful? Consider the following woman, from Nedarim 66b:

A man once said to his wife, 'Konam that you benefit not from me, until you shew aught beautiful in yourself to R. Ishmael son of R. Jose.' 
Said he (R Yishmael) to them: 'Perhaps her head is beautiful?' 
'It is round,' they replied. 
'Perhaps her hair is beautiful?' 
'It is like stalks of flax.' 
'Perhaps her eyes are beautiful?' 
'They are bleared.' 
'Perhaps her nose is beautiful?' 
'It is swollen.' 
'Perhaps her lips are beautiful?' 
'They are thick.' 
'Perhaps her neck is beautiful?' 
'It is squat.' 
'Perhaps her abdomen is beautiful?' 
'It protrudes.' 
'Perhaps her feet are beautiful?' 
'They are as broad as those of a duck.' 
'Perhaps her name is beautiful?' 
'It is lichluchith.' 
Said he to them, 'She is fittingly called lichluchith, since she is repulsive through her defects'; and so he permitted her [to her husband]. 

If Lichluchit (Hebrew: Cinderella) were not an Israelite woman, and was captured in a battle, could someone take her as a wife, under eshet yefat toar?

Now, beauty is admittedly sometimes subjective. There is no derash I am aware of which places requirements of the beauty, despite it stating אֵשֶׁת יְפַת תֹּאַר. Indeed, the Sifrei explicitly states otherwise:

מנין אפילו כעורה?
ת"ל: וחשקת בה, אע"פ שאינה יפת תואר. 

Within the universe of derash, then, had it simply said אֵשֶׁת יְפַת תֹּאַר I might have made such a diyuk. But the next phrase of וְחָשַׁקְתָּ בָהּ either modifies it, or else obliterates this as a requirement.

Ibn Ezra puts it as modification, I think. Thus, as a pashtan, he explains:

יפת תאר -בעיניו.

וחשקת בה -שתחשקנה לקחתה לאשה

Thus, she is beautiful in his eyes. One could add: otherwise, why would he want to marry her? Beauty is subjective, rather than objective.

Ramban puts it differently, and there seems to me a practical distinction here. He writes:

יא): אשת יפת תאר - דבר הכתוב בהווה.

ובספרי (תצא ה): ע

מנין אפילו כעורה?
ת"ל: וחשקת בה, אע"פ שאינה יפת תואר.

ור"א אמר: 

יפת תואר בעיניו. 

It is not (necessarily) subjective measures of beauty, like Ibn Ezra, but rather that the Torah speaks in the common case. He would likely take this captive as a wife because of her beauty, and therefore when speaking of her the Torah speaks of her as a beautiful captive. דבר הכתוב בהווה, but not that this is a true Biblical requirement.

Ibn Caspi says similarly to Ramban:

וראית בשביה וכו׳. וחשקת בה. כן הוא הדין אם
יקח לו אשה כושית וכעורה ביותר, אבל דבר הכתוב בהוה והיה זה
לעד נאמן:


and uses it as excellent proof to establish this important principle in the general case.

(One might have imagined differently if the Torah is only coming to combat the yetzer hara. What if he just thinks she will be good for child-bearing, but is not really that attracted to her?)