Is it that much of a problem to have a send button so invoices go directly to an email platform? It's done on QuickBooks so we know it can be done. I know QuickBooks is not the same as Quicken.
Why not start off with just opening the Apple Mail and transporting that invoice to PDF on apple mail. Then later on work on getting it to open with JPEG or to another email platform. Seems to me like it should be pretty easy. Maybe make that on the next update???