In general, i think that you should totally do it if you'd like to use such API yourself or have strong reasons to believe that people would like it.
Actually the binding could be provide next to the jscript API, not in replacement of the jscript API.
Yeah, that'd be totally necessary.
The big benefit of NetCore or DotNet, besides supporting multiple langage, is that it can load and use C Library almost transparently with PInvoke, which means one can use most math lib available without modifying warzone2100 or the script engine.
Hmm. Would it be secure? Like, we're spreading maps with, possibly, built-in mods in a viral manner through multiplayer games, now with an ability to execute arbitrary binary blobs from within maps downloaded from possibly untrusted hosts, how would we deal with various malware maps and mods? C is very hard to sandbox. Even though the AI script is only run on the host (unlike game rules scripts), the guest player can still open the map after the game, and accidentally run the malicious AI script.