You could generate an SQL statement (on other DBs) such as...

    SELECT word
    FROM words
    WHERE
        length(word) = N
    AND word like '%A%A%'     (if there are 2 'A' in the orig)
    AND word like '%B%'       (if there is 1 'B' in the orig)
    ...
    ...
[download]

to get all of your candidates.

Of course, this assumes that your word list is in a DB.