Say I have a simple bundle for inserting lines in /etc/security/limits.conf, it'd be good to have the bundle agent / edit_line which describes how to make the change, completely separate from the data that describes user1 gets a hard nofile of 64k.

There's lots of ways to achieve that from just doing selective usebundles from various bundle files containing only vars to more flexible approaches; In our deployment we've provided this as part of our bundle framework (we inject the parameter data via modules protocol - so a box in location A applies different data than a box under line of business B), they both reuse the exact same (comprehensivly tested) code.

This means no code release for a data change. No need to train everyone in CFE syntax just to allow an app developer to express that user c on box d is allowed more open file handles.

The point though is that It'd be good to have as a first class language feature instead of each cfe site reinventing a separate framework for the same functionality.

Haven't had any hands on with 3.5 so not familiar with that, but better print debugging isnt where I was going with the idea. I want to be able to step through a bundle, I want to be able to break when global class X is set. I want to then be able to set class X while stepping through. Kinda like making debug logging level interative and with higher signal to noise ratio on screen.

If there was language support for unit testing my bundles I could use that to reason about what I expect to happen. Diego Zambonis book proposed one way to do that with the existing facilities but its just a proof of concept, e.g. it cant guarantee environment cleanup after a show stopping error in a test.