I found this article on "Empire" (The Irony). It doesn't look like an interview, more like a transcript of some commentary or behind-the-scenes footage, but either way, we have a quote from Gareth Edwards, Director of Rogue One:
Edwards: It was definitely a deliberate thing to have diverse characters. Because Star Wars is so diverse – they have walking carpets and droids. It's about as diverse as it gets. But what happened is things evolved. Like, you know, you've got Star Wars and you've got to make a film [set just] before it. So what do you do? One of the things you can do is look at the things that inspired George and go back to them and see if you can branch off in a different direction. One of the main things that inspired him was Kurosawa's The Hidden Fortress. And there were two characters in particular that inspired C-3PO and R2D2, and they were these Japanese slave-servants who bickered all the time. And I was thinking, "why don't we just do that but without making them robots?" So that started off being Baze and Chirrut.
He literally looked at The Hidden Fortress, looked at C-3PO and R2-D2 and went "I know... we'll do the same thing. But not robots."
Interestingly, Chirrut and Baze weren't even in the original lineup of characters, that honour first went to Moroff (Originally named Senna) and Lunak, which were this pair of furry creatures clearly designed to imitate the Han/Chewie dynamic. After those characters were cut and Chirrut/Baze were brought in, they went with the Threepio/R2 dynamic instead.
Bonus fact: At first, Chirrut wasn't even blind. The character went through a number of revisions, and Gareth Edwards allowed Donnie Yen to flesh out the character, which is when Donnie suggested making Chirrut blind, amongst other things.