Re: Sounds like a good idea
C already has bit-size designators within a structure, like
unsigned int nine_bit:9;
etc. - it'll get padded out to a power of 2 [probably native word size] but you can modify that with packing and so on.
Thing is, as I understand this can cause a bit of trouble with endian-ness so it's almost a YMMV kind of thing. As a result I end up hard-implementing the non-standard integer types with macros so that it's consistent regardless of integer size or endian-ness. [portable structure definitions that compile on x86, amd64, ARM, _and_ an Arduino, using those binary structures to transfer data back/forth between all of those]
having the designated _ExtInt support would probably help a LOT.