[exim] greylist rate limit hack - feature request

Hi;

    This may be a stupid question but...
We already have rate limiting, which can act in a similar way to 
greylisting, eg. tracks connections, keeps count, defers etc.
Could this code be hacked to produce a greylist style feature ?

So instead of "allow mail through, until a time / number limit is
reached, then defer"; we have "defer, for a period of time, then allow
mail through".

Disclaimer:
I am not a coder.

rgds
neil