If you know that native format is not compatible, why do you use it? :-)
I can't but see that you need to use character format.
When it comes to special characters, you don't give any example of what is special to you. But one thing that can be problematic with bulk load is code pages.
I have an article on my web site, http://www.sommarskog.se/bulkload.html, which may be helpful to you., even if I'm not covering Sybase, only MS SQL Server.