Is your feature request related to a problem? Please describe.

@anna-x-li has added new features allowing for retrofitting of Assets, in PR #115 . This currently only works for single-stage models, and will throw an error if configured differently. We should extend this to multi-stage cases.

Describe the solution you'd like

I think Anna's current solution will extend easily to multi-stage models, but someone needs to take the time to correctly pipe information about retrofits in stage N to stage N + 1