C2 is still in development [0] and in my opinion sticks most closely to C in spirit. It seems like the best way to modernize a C project incrementally because it sticks most closely.

I haven't tried any of these languages though, I genuinely enjoy writing dumb-as-bricks C despite all the downsides. Call it Stockholm Syndrome or whatever.

[0] http://c2lang.org/site/introduction/evolution/