Could you use a Customer Feedback Form (CFF)?This is just an idea and may need to be tweaked depending on your use case/workflow and I will put a disclaimer here that I have not tried this, but in theory it could work.
1) Create a CFF with questions for the fields in the email that change (the variables such as Dates, Name of Form, or what ever.)
2) In the ProntoForms Web Portal, launch the form from the URL and fill out the details (answer the variable questions) and press send. This would send a copy of the customized email to all users in the destination.
Use DREL to pull the details from the form into the customized email.
Create an email destination(s) with the users you want to send the notification to.
These three documentation links if needed:Email Data Destinations: https://docs.prontoforms.com/1374411/Content/Published/217500028_EmailDataDestination.html?Highlight=Email%20Data%20DestinationDREL: https://docs.prontoforms.com/1374411/Content/Search.htm?q=DRELCustomer Feedback Forms : https://docs.prontoforms.com/1374411/Content/Search.htm?q=Customer%20Feedback%20Forms
Meanwhile, we will log a Feature Request on your behalf.