User should be able to see a collected list of warnings/errors after a batch open.

When using batch --open from the command line, there are potentially many files being acted on, and many more lines of output.
Non-fatal warnings/errors can easily be lost in the output, so these can be repeated in a group/list after all other operations have completed.
In the case of non-headless operations, they could appear in a (scrollable) dialog.