I would like it if EU tax could automatically be applied to user upgrades. This law means we should be adding tax at the rate for each country.
Shopping cart systems such as Woocommerce have identified this problem and introduced plugins to deal with it. There is what appears to be a very useful on line accounting system - http://www.taxamo.com
They have an online system for VAT MOSS transaction accounting. I believe they cooperate with various software and shopping cart developers to help integrate into their system.
On my other site, I use Woocommerce shopping cart and in partnership with Taxamo they developed a Taxamo plugin which makes it very easy as taxamo collects all the information and exports in a format acceptable by HMRC.
At the very least we need an addon that can report and log the location of anyone who buys an upgrade.