This works for me ...
RegExp:
(?i)(\s)f(?:ea)?t(?:(?:\.?|\s)|uring)(?=\s)
Replacement:
$1feat.$2
Example:
$regexp('Mrs. X FT. FT FEAT FEAT. FEATURING Ft ft Feat feat Feat. feat. Featuring featuring Mr. Y','(?i)(\s)f(?:ea)?t(?:(?:\.?|\s)|uring)(?=\s)','$1feat.$2')
From:
Mrs. X FT. FT FEAT FEAT. FEATURING Ft ft Feat feat Feat. feat. Featuring featuring Mr. Y
To:
Mrs. X feat. feat. feat. feat. feat. feat. feat. feat. feat. feat. feat. feat. feat. Mr. Y
DD.20091220.1124.CET