With Hen Gaidth sword, you can play an extra Duchess' Informant. Better that than trying your luck with Mr Vigo if you ask me. You can even play an extra Cantarella. This combo is gonna be nice with nilfgaard spies.
If NG had 3 more draw cards then double or triple canterella would be excellent (repeat deploy plus the sword.) The issue is there are 25 cards. 2 viper witchers plus what's his name (pick 1 of top 3 to discrard,) takes them down to 6. If they use Witcher trio and you use multi canterella after then you could actually gain CA. The problem is you need access to all your draw cards and cyanna. I agree there is potential, but it is narrow.