I believe the timestamp issue has already been resolved. It now gives a green light warning, but not an actual error. :)
pcdsrvc.pkms seems to be an exception to the rule, but it is very rare. The only other driver I see with a four letter extension is pcdsrvc_x64.pkms, the same company. There may be others I have not seen; I have not sorted through all 3,119 drivers. 
I do not know whether it is necessary to make it possible for four letter extensions to be accepted. It is really your call.
