Thanks, maacruz. I've also sent this question to libfprint mailing list and I've got this:
So I think you're right. Honestly I have no idea about how to do what you've suggested, but I've been searching for articles related to recompiling kernel and bookmarking them to digest later. Could you give me any hints or links that could help a newbie like me complete such task?

PS: I have found a link which could be useful, but I'll give a further read later: http://talk.maemo.org/showthread.php?t=34901