Having a large body of existing packages would be nice, but if this can be used with a private repository, it's be hugely valuable to me even if it had no open source packages available at all. I work in a corporate context where projects frequently have multiple complex internal proprietary dependencies. The hacks and workarounds I've seen just to get a sane build up and running in this context are unbelievable. After having used Cargo for some personal projects, I yearn for a similar tool in the C / C++ landscape.