Chip,
My preference would be having all the glass parts come in white that's good enough to use as a base color without having to spray white on top of white.

I'd prefer that all the foam parts come unsheeted with each panel coming in a separate shuck, not both panels cut out of the same shuck. That way, I can build them as light and straight as my skill level and pocket book allows.

Then I'd want molded in reference marks on the fuse that show where the designer intends for the wing and stab to be mounted.

Formers can be pre-cut or printed on paper as long as they're reasonably close to what they should be.

Finally, a minimal instruction sheet that tells me what the dihedral is supposed to be as well as suggested throws.

Assuming all of the above is of good quality and light enough to make weight, I'd be happy. There's nothing more frustrating than getting a plane from halfway around the world that either has components that are too heavy to make weight, are damaged, and/or crooked. I've experienced one or more of these flaws in the last 5 or 6 planes I've built from various manufacturers all over the world. In each case, I had to dispose of and replace something or other to either make weight or make it straight.

Verne Koester