[Exim] Reject spam after DATA, Multiple user Preferences

Hi,

We're currently rolling out Exim/Exiscan configurations to customers,
and are looking at adding SpamAssassin to the mix.

According to the Exiscan documentation, to implement per-user anti-spam
preferences, you can either only accept mail with one envelope recipient
at a time, accept envelopes with multiple recipients only if they all
have the same group antispam profile, or always accept after data.

What I want to know is if it is possible, in theory or in practice (And
indeed, if anyone is doing this I would like to know how): To run
antispam checks for all users receiving the mail according to their
personal profile, reject the mail if it's marked as spam for some users,
possibly listing those users in the rejection message, and then go ahead
to quarantine/forward/send the copies of that mail as appropriate? What
issues face an implementation like this?

Best Regards,
-AL.