Charliehall,
I was under the impression, having once asked this as a practical shailia, that the accepted psak is that a woman can lain megillah for a man. That it is normally avoided is a chumrah which is choshesh that a woman only has a chiyuv shmia and not kriah and therefore can only be yotzie a man’s chiyuv shmia and not his chiyuv kriah.
In other words everyone holds that woman can be motzie a man in megillah, the issue is only whether or not it is ideal.