With Windows 10S being store only, it is now the ideal time to put eM Client on the store, Win 10S is going to be used in certain environments were a high quality email client will be necessary and really it would serve you guys well to be the only real option on the store (even if it means bumping the price compared to what you sell on your own site).
The Win32 bridge allows using existing desktop apps so there is no need for a rewrite and the Win Store is actually quite good for license management, clean install and uninstall plus crash data for developers.
Contrary to what some think or hope the Win Store is not going away, it’s Microsofts bulwark against future Android PC’s they need to make it work otherwise its not good for the long term future of Windows.