A nice big ecosystem with both a simple ABI and type system, but with a nice safe type system that doesn't need manual memory management. Interfacing to C libraries from more modern languages is generally a huge impedance mismatch and necessitates some kind of wrapper. Also C libraries vary wildly in how they are built, if they use macros, how difficult their headers are to parse, etc...

Linking to Go libraries from a certain type of language could be super easy and the libraries would be nice enough to use to not need a wrapper layer.

I talked about that because IMO a really important part of having a usable language is an ecosystem, and if you're going to start a new language today piggybacking off of Go's sounds like a good plan.