Kman,
So the real question you should be asking is: Does EV support intelligent filtering?
The answer here is no. Version 7.0 (due by the end of the year hopefully) will incorporate a lot of this, but it's not here today.
So here's what you do in the meantime, and yes, you'll need EVPM to help you out here. The strategy here is to figure out how many different categories of retention you need to have, and then to give each retention category an easy to understand folder name under the inbox of every user's mailbox. You'll have to depend on each user to push the email in to the right folder (which depending on your users should be easy/hard).
Create an EVPM script that creates a folder, and assigns an override retention category to the folder. You only need to run it once on every enabled mailbox.
As far as spam and stuff, don't worry about it. Users usually delete it within 10 days, and outlook and hopefully your exchange server is already filtering that stuff.
micah