Also, check out the Content Collector products -- I believe these were formerly the 'CommonStore' products.
Damn, that's sad. CMOD is the perfect place for eMails -- uses data compression, consolidates multiple eMails into a single object, could store attachments as resources...Am I missing something?
If you are not afraid to run OnDemand also on Intel, you could setup a second server on that and use full context indexing services to index the archive on AS400.