What does ASSP X use to get the messages to the spambox? Does it take the messages from the spam collection folder? Does it use spamlover/testmode/ccallspam to collect them? I am curious to know.
I noticed that ASSP X does a lot of work in exim.conf, perhaps you could also address the issue of sub-addresses in exim? I have an enhancement request open here:
http://bugzilla.cpanel.net/show_bug.cgi?id=5292
It should be pretty straightforward in exim, the only problem would be writing a frontend that would control the filters for subfolders and such.