Controlling extended classic

We are using the Extended classic scenario in SRM 5.

A requirement has now surfaced where all catalogue items should be processed within SRM PO wise so when the cart is approved it reacts just like extended classic where a copy of the PO goes to R/3.

Free text items once approved should invoke the classic scenarion via Badi BBP_EXTLOCALPO_BADI.

Our problem is that it cannot destinguish between catalogue and free text items and as we are not using R/3 products and types we can only use the product category section of the method, but as catalogue items could have the same category this causes a problem as we do not want to add categories specific for catalogue shopping and the decoupled scenario does not suit the model

Can anyone help with a suggestion we have also looked at using the the badi BBP_DETERMINE_LOGSYS

Tom