Kaidan DOES have Ash's lines if you use the "Play as femShep" mod.
(That is a joke.)
It's likely a LI thing, in terms of story. If you're wanting Kaidan to have Ash's lines when you're playing as maleShep, writing such a mod might be relatively simple for someone who's done story edits...but I'm not the guy to do it. (I'm more of a fanfic writer, though I'm considering writing a mod if I can find the time.)
It might even be possible with creative use of the Save Editor...if the Force is strong with you like that.
