I think the #include extension could make vec_vec / vec_list / lst_str type nesting more natural/maybe more general, but maybe just my opinion. :-)

I guess ctags-type tools would need updating for the new possible definition location. Mostly someone needs to decide on a separation syntax for stuff like `name1(..)=expansion1 name2(..)=expansion2` for "in-line" cases. Compiler programs have had `cc -Dname(..)=expansion` or equivalents since the dawn of the language, but they actually get the OS/argv idea of separation from whatever CL args or Windows APIs or etc.

Anyway, might makes sense to first get experience with a slimcc/tinycc/gcc/clang cpp++ extension. ;-) Personally, these days I mostly just use Nim as a better C.