Thank you @Stuart Wepener for reaching out and using the Microsoft Q&A Platform.
Post discussion with our internal team it has been called out that capability for templates called what-if which is in preview can help address this scenario. However Blueprints definitions currently doesn't support it but will eventually migrate to template/template specs, at which point we will be able to do this. Sorry you might have to wait until Blueprints definitions will migrate to template , current ETA for this migration is tentatively scoped for March 2021.
Hope this information helps, please feel free to revert back if you have any further queries. Thank you