Initial discovery and discussion: https://ginkgostreet.atlassian.net/browse/CA-137
My current thinking is this: if we weren't looking to create an "invoice" here, the reminder email could be written vaguely enough that we could get away with using the default mailing tokens, particularly if the Primary Contact of contact has the org listed as their employer. As it stands, we'll likely need to create some tokens to get the actual membership.
The basic Most of the functionality for option #1 exists out-of-the-box in CiviCRM, the exception being the need for membership tokens that target an organization's membership info rather than the contact receiving the reminder email.
Mosaico Message Templates is already installed, so "importing" a Mosaico template into a scheduled reminder is as easy as selecting it in the "Use Template" drop-down menu of the Scheduled Reminders config screen.
There is an extension that adds mailing tokens for contact info via a relationship to the recipient. There are relationship tokens in there already, and using a "Primary Contact For" seems viable.
Alternatively, we can traverse the conferred membership record to get to the Primary Member Record.