The Clone Wars (the CGI one) series is still canon as far as i know and has Headhunters, though perhaps the old version of the Headhunter is now Legends content.
The quad lasers still makes sense even if the ship isn't a proper X-wing... you just have 4 high power laser cannons.
Looking at the video, the wings do look a bit like they'd split, the seam is just nigh-invisible.
Hm, I don't remember seeing headhunters in Clone Wars, but I watched all of it in about 2 weeks so I could just have forgotten. It's the TIE Fighter/XvT game version that I was thinking of.
I don't think the seam is a problem, but the engine. X-Wings have one engine per arm, it would be odd for this one to split, though I suppose it could.