I don't want to be the smart ass that did nothing and complains
about what other did, but I'll be it anyway.
It doesn't look very scalable to me to implement various versions
of modules with various memory management schemes. Inevitably,
these will have different subtle variation in semantic, different
set of bugs, it is twice as many work to maintain and so on.
Have you tried to explore solution where an allocator is passed
to functions (as far as I can tell, this wasn't very successful
in C++, but D greater metaprogramming capabilities may offer
better solutions than C++'s) ?
Another option is to use output ranges. This look like an area
that is way underused in D. It looks like it is possible for the
allocation policy to be part of the output range, and so we can
let users decide without duplication bunch of code.
Finally, concepts like isolated allow the compiler to insert free
in the generated code in a safe manner. In the same way, it is
possible to remove a bunch of GC allocation by sticking some
passes in the middle of the optimizer (
