>> I think there’s currently no easy way to cross build a full GuixSD >> anyway, like ‘guix system build --target=mips64el-linux-gnu’ (the >> --target flag doesn’t exist yet). Or did you experiment in this area?
I'm operating under the assumption that when using the --target flag packages aren't substituteable (since cross-compiling a package will likely not yield the same result as natively compiling it) in which case the --target flag would only be useful for either bootstrapping or optimizing guixsd for an embedded system or something like that.