I just think Ashe is good friends with Vaan, she was friends with Balthier as well but i think they grew apart to far. She still seems to be good friends with Vaan in Revenant wings, where as she's not really close to Balthier any more.
I wanted Ashe and Vaan I had to admit, but i warmed to Penelo in the end, she's very caring and mature for her age and her and Vaan really do seem to be a done deal.
Vaan and Penelo also seem to be a bit like Balthier and Fran's proteges, so its fitting that they get together.
I'd like to see Ashe/Basch get confirmed but if thats to crack then for Ashe to marry Al Cid and for them both to start fixing the problems in ivalice.