Some background. We use the Cases module for all of our service calls. When a technician is on site, they complete the work - enter in the parts they used in a subform and change the case status to "in review". This needs to automatically generate an email to the customer showing the work performed. This is not an invoice, but rather an initial list of the work done. 

Here are the issues I'm running into:

1.) I cannot include the subform into an "email" template.

2.) I could merge the subform into a "mail merge" template, however the Cases module isn't a supported module for mail merge.

I've thought about running this through standart workflows, through zoho flow, through writer. All keep coming back to either I cannot have a subform in the email template, or I cant access the cases module in any of the other options. 

PLEASE give me some ideas of how to accomplish this task. Doesn't seem to be too crazy, so I'm not sure why there isn't a simple solution already in place. If it requires a custom function - I'm ok with that as I have some basic knowledge of creating my own custom function scripts. 

Thanks