I'd like to see some additional fields in the customer card, eg:
Email subject line:
I have some clients (eg insurance companies) that request a particular reference code (eg case number) in the email subject line for their internal routing.
GST included / excluded:
It's only a matter of time before I trip up, and charge GST on top for residential customers, or include it for commercial ones. I'd like to set this for each customer.
"Contact-based preferences: email subject line, GST included / excluded"