If there is more than one .eml attachment, the text for both should show -- also attachments inside those .eml's will be pulled out into the attachment pane.
Don't know if I'll be able to compete with Microsoft -- I hear they have a lot of developers / managers, and plenty of money to pay them...
But I thought being able to view attached .eml's, as simple as possible, was a worthwhile goal (also winmail.dat attachments -- a continuous source of pain when mixing Outlook / non-Outlook mail apps... except Aqua).
I think my real competition is the new generation of mail apps for Android (seems there is a new one every week), like My Mail, Fluent Mail, Cloud Magic, etc.