All right, I have installed the new UruExplorer.exe on the Shard.
You will automatically receive it on the next login. I couldn't use the new UruSetup.exe, as that one does not support logging in to a server. But the good news is that the hacked-together widescreen support (through our own custom launcher modifying the dev_mode.dat) still benefits from the game now taking the aspect ratio into account.
I walked a few ages and everything seemed alright. If someone here has Windows 10, it would be great if they could test whether this fixes the cursor issue. If you notice any new problems, please speak up!
Also, I noticed something funny... Chogon even mentioned the Teledahn problems that we have a fix for in his announcement for the beta version.