I'm giving up on procmail.
You shouldn't have to give up. I suspect a lot of people use procmail just as you have described you want to do. It is the simplest implementation of SpamAssassin, ClamAV, and Postfix, and works great. You shouldn't be limited as to whether you use it site-wide of user-specific.
I use procmail to call ClamAV for site-wide analysis of all email, and then have .procmailrc files for each user that I want to use SpamAssassin. At this time I'm using site-wide SpamAssassin rules, but you don't have to do it that way.
Everything else you try will be more complex than using procmail. I think you should get procmail sorted out before you try the others. - John