May and Dawn suit Ash very well.
Eh, they're quite different in many ways. Ash is generally related more to struggle and a slight liking of grit and so on, etc. Part of the problem is that May for instance can seem to 'suit' just about anyone, which might be part of why they're known to be shipped and attracted to just about anyone. Given how they tend to be in that sense, Ash, who's generally more adamant on his journey, might seem a bit derailed by having to get too close to such people, apart from occasional romantic vignettes.
There's not that much room for it unless they had a protracted return, as someone like May returning just for a brief coupling thing, despite being considerably different from the tone of the anime at present, might be problematic, although it might perhaps work more with Dawn, who's a bit more like an eclectic collage of the traits of some of the girls previous to them.
Sure, Ash x Misty is cool, but a Pokemon coordinator fits Ash much better than a gym leader in my opinion.
To be fair, at this point, co-ordinator, performer, etc., are blending into each other a bit, so in that sense it might make slightly more sense to opt for someone who does at least engage in training and so on, for display purposes. The problem there is that Misty isn't generally portrayed as that interested in Ash, although she rarely goes for protracted flings with others.
May x Drew is pretty much obsolete, the writers don't even care about Drew anymore.
To be fair, May has been absent for a while as well, so they could just sneak that through as a way of doing things easily without having to portray that kind of relationship in detail, which they don't seem to want to do.
As for perfect girl for Ash , I want someone cool & Badass like a Shouene heroin!
If they indeed took heroin, they could do all of that and more.
After the Serena thing, how long until the anime degenerates into soppy lines from Twilight? Ash turns into Greninja, tells Serena that she's his heroin, and then plays baseball against Alain's Charizard.
She can instantly create competition in the Anime because of Drew ! Animes like Pokemon require competition.
I mean, if they wanted to drag Drew back as well...
They probably don't want to make too much of that, but in a sense most of that arc is already complete. They could go for something relating to May casting a wish about it, possibly, and also seeing Ho-Oh, which by this point essentially means nothing much other than that they might get lucky at some point, but anyway.
Furthermore , She is the 2nd character to have a complete family ! Her family also make Advanceshipping interesting.
In terms of Pokémon, you probably don't want to make that kind of courtship process, which might be emphasised in certain more 'Japanese' anime, too much of a focus, as it might distract from the predominant focus and sense of adventure and wilderness of the series. That said, though, May didn't half spend a lot of time being forced to reconcile couples and reinstitute them, so in a sense of lot of what made her a prominent ship might now be irrelevant to people watching the anime now.