Updated Booming Blade to only be usable once per Action taken. If the initial attack was not Booming Blade for Extra Attacks, one of the Extra Attacks can be Booming Blade.
Fascinating ...
I honestly thought that all that homebrewing around bladesingers was bcs this would be too hard to implement corectly ...
It seems its not.
Now all we need is to set it like this for Bladesingers only and let it work as regular cantrip for others. ^_^
There still may be hope for patch 8. :3