This is a really strange question
Ofcourse it isn't realistic
But Squaresoft did well not to "exploit" this as much as, say Team-Ninja, might have.
I find El Ammo Bandito's "FF7 sword masculinity theory" hilarious
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Definitly not the case, otherwise the female characters would also have some other specially designed weapons of "special" sizes and/or shapes.
Tifa would most certainly be reliant on her fists to say the very least
There are far too many reasons why Tifa is the way she is
Nomura has stated he couldn't decide if Tifa should wear (mini)shorts (like Rikku's) or a miniskirt, but he went for a miniskirt in the end.
You can understand why he had thought of shorts: she is a country-girl, and shorts would have strengthened the look, noting she also has a buckle-straps, a simple ponytail, and favours simple colours (black, white and reddy-brown).
Her larger-than-average chest is more a charactertistic of her individuality rather than a focused attempt at sex-appeal.
Her top and her personality could have been far more "expressive" but they were not.
On balance, she probably has the most skin showing for any other characters in FF7 (ignoring wrestlers, swimmers, and beach-going people) which results people assuming she was designed ONLY to serve for sex-appeal.
I dont know about anyone else, but to me, she is designed for 1/4 sex-appeal, and 3/4 for personality.
But because her sex-appeal is slightly more than anyone elses, people assume that was the ONLY reason she was designed for
And cosplayers and doujinshi artists have a field-day because of the usual hentai stereotype connotations:
a sexually-appealing woman with an undecisive personality = very easily exploited
(no, I dont watch or read that kind of stuff, I just stumble across them at random. I feel so sorry for Japanese women, their society shows no respect and no remorse. It is sickening to say the least
)