This is certainly possible. Setup split with 2 rules:
- One to split off the number of pages you want for the imposed signature
- One for the rest of the pages in the document
For example, if you wanted 2 pages in every document:
If you look at the page range, it will split off pages 3 to the last (aka page -1). All Page range fields support both positive (from the start of the document) and negative (from the end of the document) numbers.
Once you have defined the rules connect the second rule back to the split node.