1. 16 bit at least . better 32 bit per color / perhaps diferent color depth for different objects/layers . It's necessary to compose objects with "Z" depth value for modern materials in CG industry / games etc. to get proper objects intersection/ a mask where pixels is "highter"

2. object/layer masks with a separate "mask" stacks + "difference" , "invert" and "lighter color" blending modes

3. auto updating bitmap fill if source file is changing

4. "skeletal" brushes from Expression/Design with alternating parts

5. Mesh deform for bitmaps with ability to set a curve in a picture and then deform it to appear straight

6. Scaling from a pivot , center of transforms


I loved Xara and still love for simple quick things but it's seriously behind current needs