I'd argue against that. Just because you can make a concept, doesn't make it a good one. Battlecast resembles nothing to the other battlecasts, in terms of the rawness of their designs, how tank-ish they feel, not to mention you run into the same problem that Lunar Event Caitlyn ran into, as it just didn't resonate well.
Dark Star so far works best on monstrous entities, with I think it's biggest weakpoint being Varus, albeit a good skin regardless. Varus still resonates with a corruption theme, as he himself is in the process of being corrupted. Orianna works well as well, because she can be seen as a monstrosity base-wise, something no longer human, but a machine. They still resonate with the theme, Ahri does not. Even if she feels like a monster in the inside, her correlating visuals on the outside give no indication of that, unlike Varus.
Deep Sea Ahri, even aside that it just doesn't look like a good skin, makes no sense at all. Why are we giving a Champion a water themed skin, when she is the furthermost away from water. Fire makes sense, one because it was a joke on Firefox browser, but the fact that her visuals are very firelike in general, there's a good visual connection.
Syndra, although I'm not a fan of it, does a Water theme well because her visuals are much more fluid than wispy. Her Ult showing streaks of water flying towards you is a good connection between theme and visual, but I doubt you can do the same with Fire, to the same degree of well-doneness. I think it's one of the main downsides of getting a Pool Party Ahri, that it's hard to make wispy looking visuals look good as water. The SFX would honestly be doing most the work, splish splash sploosh.
Fitting a theme doesn't mean it's a viable skin. The too many concepts of SG Urgot flying around does not automatically make it a viable skin theme that matches well.
