I wish there was something better than Lua and just as "obvious" a choice. Static types, real arrays, zero-based indexing, etc.

Closest thing I've seen so far is Roto: https://roto.docs.nlnetlabs.nl/en/stable/index.html

Basically everything about this looks great - Rust-style syntax, static type checking, sane type system, easily embedded. The only slightly odd things are that it has built in types for IP addresses, AS numbers, and `filtermap`. But I guess you can just ignore those if you don't need them.