Depends whether by "in theory" you mean,
"hey, man, anything's possible" or "with enough > effort, this could
happen". If the former, well, yes, any article could be an FA --- in the same >
way that a Muslim could become the next president of the United States of America. If the
> latter, then, no, not all articles could become FAs. That's one of the reasons
why GA was
set up, and one of the reasons why GA is such a failure.
The rules for FAC specifically say that FA status can't be refused for
a reason that can't be fixed, so by the letter of the law, all
articles can become featured with enough work.