Well hello again! Nice to be back :)
I actually like Basil, so I say let's go for it! Other ones I like (maybe for a middle name) would be: Forrest, Leo, Orion, River, Sirius, Sterling and Jasper.
I think using initials would be the best bet seeing as there isn't any names that relate to Duncan. Here's a few I know of, I'm open to almost anything! We could tweak them too!
D- Danielle, Delia, Darine, Daisy, Delaney, Deirdre, Destiny, Desta, Diamond, Diana
A- Abigail, Alexandra, Aline, Aria, Anna, Arabella, Adriana, Amber, Alba, Ada, Adela, Amelia, Aisling (There's so many A's to name, any ones you like in particular?)