How to use the output of one run as input to the next in QGIS batch processing?

Question

I'm trying to do a series of buffers using the processing batch interface, and I want to use the output of the first run as the input to the second (and so on). But I can only pick an existing file or open layer as the input, and since the last run hasn't finished yet it doesn't exist.

I'm pretty sure I can knock up a script to do this but it seems like the sort of thing you should be able to do using the batch processing interface so I'm wondering if I missing a trick?

• Herbert Santos: The batch process does not allow this type of execution because all inputs must already exist before starting the process. What you need is a looping process, possible only through a script.