I agree custom email template would be very useful. For this reason I
don't use the feedburner email system, but I use the same email system
I use for my newsletters because they have the ability to auto
generate emails from an rss feed and they provide full control over
the content. However, it ends up costing me extra to do this because I
have to pay per email or have a limited number of subscribers for all
emails before I have to upgrade to the next higher package to have
more subscribers. So I really would like to see feedburner give us
more control over these emails.