Everything should be in "human readable" or text format, no binary: SVG for image, xml for object/project description etc...
So it's easier for revision control system, team working, re-use, merging, editing, archiving, etc...
Yes, especially cap files
No binary caps, so there can be no such thing as an irreparably corrupted cap file, and an enterprising individual could even make some type of script that automates some tedious cap editting process
Also, unrelated, but what about giving the sdk a dynamic combo box option for the acetable that allows users to have the choices change the way they can with private variables and global variables. There's a few times when making a plugin this would have been a perfect fit, and I had to compromise better usablility