Boooooooth >
I personally think making Jaesa romance-able to both sides would actually make your choices mean less. You go into the SW knowing that being good will not net you a romance with her but you want to have a romance with her. They're forcing you o pick a path and live with the choice, to strip away the consequence would make the choices you make up to that point meaningless. In my opinion.
Also, as I said muuuuch earlier in this thread, good Jaesa would not engage in a romance strictly based upon the fact that she is still a jedi because you did not turn her. Think of her as "a jedi in the company of a sith" where as evil Jaesa gives into things like lust and greed thus making her...in some bizarre way, the perfect candidate for a relationship.