I am also an ATCO and a Met Observer. I work in an area of the UK where the worst and most changeable weather occurs. When the wx is unstable, highly changeable or just downright nasty and on limits, the vis/wind/cloudbase/rvr change so quickly that the ATIS is always out of date. When it is really bad the wx can change to outside limits during the time it takes to physically read the wx over the rt to the aircrew!
In my opinion real time updating of the ATIS is fine so long as the ATIS letter is only updated for significant changes. (A significant change is defined in the UK documentation somewhere and if you wish I will try to find it later.)
Ultimately the the best real time met info in a changeable environment is that which can be passed on the rt at the exact time required for the captain to ascertain whether or not they are within limits.