Hmm...perhaps if you use a separate sorting system for farms output, with no entry into the main network, but only into the subnetwork (or separate network) that handles farm output with only "preformatted" barrels or storage modules as storage. I don't know how ME interfaces behave if there is no valid storage destination for something you pipe into them. If they won't accept those items, TE itemducts won't see them as a valid destination, and then you can use an itemduct set to "dense" mode to route the overflow into a trashcan or a condenser. You can then use storage buses to access either your barrels, or the subnetwork's storage modules through an ME interfact, from the main network.
Thanks for the reply. I don't know how the interface will behave either, but I'll find out as I'm currently setting up my storage. I have a feeling the internal [8-slot?] capacity of the interface will fill up before denying any items. Hopefully not. Your mention of the condenser got me thinking more about maybe letting AE process overflow. In Agrarian Skies [AgS], you can compost various items to make dirt. I hate just throwing things away, so I may setup a sorting system where compost-able overflow goes one-way and everything else is sent to the condenser.
The real problem I recall with letting AE process overflow [experiences with 1.5 AE, and aside from the wasted power drain] was that it simply wasn't fast enough if too many items start to overflow. I recall having 3 diamond chests and a condenser setup for overflow and it was barely enough.
Edit: yup, the 8 slots in the interface fill up and then the interface starts refusing anything else. I can setup a duct to take care of the overflow before the AE network, but then it becomes either/or. Either the items overflow into the AE network or they are totally excluded from the AE network.
The other problem is once the interface is full of items it can't do anything with, nothing else gets passed through. I wonder...I may be able to duct items out of the interface and into a void. Depends on which system is faster AE or TE3 as to who gets the item. I'll have to test this.