Let say I want two distribute two(or more) implementations of a library
with the .mli for all ...

Is there a way to choose the implementation at link time ?

Lets say I have a.mli compiled to a.cmi and a1.ml and a2.ml

I think (did not test) that putting the cmos in separate directory as
a1/a.cmo and a2/a.cmo should allow the choice using the -I option ...

Any better solution (no dynlink, I want also native code) ?

Thanks