Interesting. It could be a nice bit of local flavor, but could also be overdone. I don't think readers want to do a lot of arithmetic to understand what's going on.
I'd be tempted to invent some calques, explain them in a footnote, and not rely on precise renderings. E.g. for base 7, maybe we use "sundred" to represent 49. Characters can explain that a city is a sundred leagues away, or that something costs three sundred pounds of gold. Pedantic readers can work out exactly what that means; everyone else can just take it as "kind of a hundred." As readers, we normally just need an idea of magnitude.
(You could use your conlang's terms, of course. But I think readers' patience is limited. E.g., in the Elder Scrolls games, I'm fine with the days of the week being Sundas, Morndas, Tirdas, etc.— it adds color but sounds familiar. The month names are less successful. "Morning Star, First Seed, Rain's Hand"... they're fine for citing a date, but don't expect me to remember their order or even what season they're supposed to be.)