It's my understanding that you can do this already - but it can be complicated. I've done it by "generating merge fields" for all the processes involved, then selecting the fields I want from each process and pasting into a new document.

The tricky part is that some fields seem like they're named the same, but are actually different. If you have "shared" fields (these appear at the top of the generated merge fields doc, in a section called "shared questions"), those are the same field for all processes. There are also certain system fields (like award amount) that are the same for all processes. But any other field that you created has to be copied separately from each process, even if they contain similar information. You can double-check whether two identically named fields are the same by right-clicking on the merge fields to "Toggle Field Codes". You can also right-click again to toggle them back.

Example: in most of our processes, we used a field called "Final Project Description" in the final report; however, in one process, we used a separate field called "Final Narrative." (We didn't rename it - we actually created a new field. Oops.) For a report of narratives that I built the other day, I had to copy both those fields into my document side by side so that the narrative for each organization would show up in the same spot in the report.

Clear as mud?!?

Here's an example form that works across all of our processes: https://basecamp.foundant.com/eco_player.php?id=520