We could change secrender to create Jinja2 variables for every top-level key in the YAML file, and get rid of the root variable idea. The -r option could hang around as a way of renaming variables as opposed to a way to specify the root variable.
Then we could reference {{contractor.name_short}} from a file like:
project:
name_short: Example Project
contractor:
name_short: Example
support_email: support@example.com
Capturing @woodt notes from a side conversation:
Then we could reference
{{contractor.name_short}}
from a file like: