I suspect that a large number of maxima users run Windows. (probably there
are download statistics to tell us).
I don't know how easy it would be to make your design work on windows, or if
it would be less work to get (say) GCL or CLISP or whatever future
"standard" common lisp on windows is used, to just call LLL in another
library.
I think that loading NTL or GMP into such a system (like Lapack) would be
neat. SAGE tries to do such things too.
RJF