Okay, so my thoughts on Mythril Pyrotechnician, the character:
* At first I got the impression that this was the return of Zelda / Shiek. Apparently they do share some normals, but we'll simply have to see how much they share.
* I'm going to go on a limb here and say: same general rules as for any swordie. It's difficult to tell how they'd play without seeing the Sakurai Presents just yet, but chances are pretty good that they'll be much more in-your-face and perhaps have Specials that encourage mind games and switching consistently between the two. Some of those are going to be commital, which is where the normals likely come in to cover those. Another weakness might be that they're somewhat tall but also light - probably not as light as
and
though.
* As someone who's never played XC2 or any XC game, I'm going to base my opinions of them entirely on if the duo can out-hype Shulk in gameplay. Or have some disrespectful kill option off stage like the DBZ teleports Mythra does (The Photon Edge).
* Nah seriously, good for Sakurai and co. to bring a twist. A ton of people were expecting Rex like crazy, and I'm presuming that Sakurai had a good reason why he's "relegated" to FS material. Going out on another limb here, he tried to imagine Rex + Pyra, but couldn't get the modelling to work.
RIP Rex and Elma though. Gone but never forgotten.