Thinking on Mattel TMNT:

 I got the Kid Core Batman figure. Review will come soon. It made me think: Mattel could do a Kid Core TMNT like that. 

I mean let's use Michelangelo as an example:

Give him the kid core DC articulation... since he's a turtle, ab crunch isn't needed here. Picture a 5.5 inch turtle with the kidcore DC articulation. It would almost be similar to the Playmates TMNT, neo vintage thing that they barely tried.

You give him a rack with molded weapons a la Playmates. 

For Shredder you go 6.5 inches (same height as DC kid core Batman) same articulation with cloth tunic and cape.

The collector version can come with better accessories, extra ankle articulation, painted weapons, swappable hands.

Make heads compatible across both lines. That way kid core Michelangelo has one expression and collector line Michelangelo has a different one. Also, the collector Mikey may have real chains on his nunchucks, but he doesn't come with kunai, shuriken and spinning nunchucks like the kid core does.

By making both lines the same scale, they can produce kid core playsets and collectors will get them... (and some will dekidify them via paints and 3d prints)... also having an Affordable Party Wagon made like the Slambulance in size would kick so much ass, it's ludicrous. 

My biggest fear is that Mattel has slowly Hasbroizing their lines. 12pack maybe a few others, reboot. I get having key characters available, but you can reboot the characters every so often.