Allow Excel for Mac to run .xll files
There are many .xll add-ins that work under windows, but none of these can be run natively on Excel for Mac. Using a windows emulator is painful, buggy and sometimes slow.
This would allow us to port add-ins made with .NET and Excel-DNA, like SeoTools http://seotoolsforexcel.com/ and http://community.seotoolsforexcel.com/t/cannot-install-seotools-on-mac-help-please/126.
With .NET core and Xamarin supporting the various Excel platforms - Mac, Android, iOS and UWP - the only part needed is proper .xll add-in support in Excel everywhere.