@Mark T
Thank you for your time and patience throughout this issue. I received an update from our engineering team and will post their response below.
Update:
As of right now, here's a full list of properties available via Graph API for Access Packages:
https://learn.microsoft.com/en-us/graph/api/resources/assignmentreviewsettings?view=graph-rest-beta
Coming soon:
"We're soon going to expose the creation of access reviews on access packages within the access reviews experience, with all the options that you have for groups and apps. A private preview of this feature will go live in the next few months, and will likely give this customer all they're looking for."
If you have any other questions, please let me know.
Thank you for your time and patience throughout this issue.