I think Construct Animate would greatly benefit from animated SVG, and drawing tools that would allow you to draw vector images directly onto the layout whilst in the layout view. Also tweening SVG images would be an amazing feature!
Tween animation is great within Constuct, but it should definitely consider the type of animators that hand-draw.
I don't have any suggestions, but I do compare Construct Animate to Flash, and I understand that many animators loved Flash since you just simply "draw, then keyboard shortcut for a new frame" repeat these 2 steps over and over, maybe drawing on a separate layer here and there. Quick and easy. Construct doesn't work like this, so it's more about adding sprites and positioning them and tweening, rather than painting a picture with some drawing tools and then adding a new frame and continuing to draw.
Another way to think of it: Sprite's are like Symbols in Flash. Some animators didn't use Symbols, as the animator simply drew their animation using only layers and frames.
So yeah, I would imagine some animators would feel it is too methodical to do ALL of the drawing as separate sprite objects. And too long-winded to have to import your drawings from another software. Other software would offer direct drawing capabilities. I think Krita is free and offers animation along with brilliant drawing tools, but it's only raster animation.
I think Construct Animate has the potential to be something really powerful!