you should (in theory) be able to link the sybase code/libs statically into a shared XS lib (i.e. Sybase.so)
Yes - that struck me, too. To take the point a bit further, I believe you should be able to build DBD::Sybase against either a static or dynamic sybase library (the choice is yours), irrespective of whether perl's "libperl" is libperl.a or libperl.so.