I’m trying to add some clipart 3DS/OBJ trees to scenes. I opened the 3DS files by drag-and-drop importing, with the result of none of the textures having path information. The whole process of managing this stuff is a pain. But frankly even with the bugs fixed and relative paths it would still be a pain, I’d vote for just vacuuming up all textures into the file all the time, size be dammed, if Rhino was able to save the resulting gigantic files faster.
I don’t think relative paths will solve this. Nothing will resolve it other than the textures either being in a specific place that you tell Rhino about, or being in a subfolder of the current 3dm file location.
But yes - I have considered the vacuuming idea.
Please let it suck… 
More information on this:
The current implementation of the way that the textures are stored in the file is not very good. For one thing, they take up more space than necessary. For another, there is some potential instability with absolutely gigantic files. Having Rhino save everything, every time would push those limits more often than they currently do.
In addition, we already get a lot of complaints about the size of the file. Now, naturally, we could turn this on by default and let people turn it off if they want a smaller file, but this would probably not stop people complaining about huge files.
Also, people equate large files with models which cannot be worked on efficiently. I’ve said many times here that there really is a tenuous correspondance at best, but that still seems to worry users.