CISCO Wap54G Omnidirection to directional

What would be the result of getting a directional antennae, and pointing it
towards the field of the omnidirectional antennaed access point,which is a bridge ?.
I have a CISCO WAP54G with 12 db optional omnidirectinal on it
and a CISCO WAP54G at the other end with normal omnidirectional antennae
as supplied out of the box.Problem is filed is too weak on the normal box, it has a connection to the high powered omnidirectional , but I suspect, theres too much reflection.The reason I didn't use directionals to start was cost,maintence issues and having to mount them outside the building.But I'm having to reconsider that, only gettting 100-200ms pings and then loses connection.I know I would be better off with two external to building mounted directionals, but if I can get away with one ?