In October I was entertaining a relationship with a pansexual man. I decided against it because I wasn't happy with my body and I ultimately didn't feel for him. He didn't see me as an other, I was just a woman to him. He was very adamant about that. Not all pansexual or bisexual people see people like us as "others." I'm willing to bet most are willing to simply see us as men and women.
As for me, personally, I think it would really depend on the FtM. I don't see FtMs as anything less than men, but I want a guy who has a guy's downstairs. If I fell in love with an FtM and he was my type and he had his bottom done, then that's wonderful to/for me.
I really prefer men who are masculine looking and masculine in personality (but not obnoxiously so), and I prefer men who are taller than me (I'm 5'9"), but I'm sure there are FtMs out there who are taller and who are really manly. To me it's just about meeting the right person and being able to have a great relationship, which includes a satisfying sex life. When I'm post-op, I really want and need the traditional male/female dynamic. That's what it boils down to for me.
I refuse to even enter relationships at the moment because my dislike for my bottom is too intense. I need my partner to "complete" me when the future rolls around, and if that person is an FtM, then I'd be just as happy as I would be with a cis man. A man is a man.