I'm an almost complete OScommerce newbie, but your related products module looks like just what I need. I'm having a headache installing it though, so your proposed install guide sounds like a great idea!
I'm comfortable with editing the php files, but am decidedly unsteady in MySQL. What is the command to load your SQL file into my database?
If you want to test out a draft install guide on someone, I'm possibly a good candidate (able to follow instructions, but largely clueless!)
PS - Also happy to try out the v4 beta.