I did a search on google for a Virtuemart bulk related products plugin and came across the project that you have recently done and though you might be interested in my small project which is very similar.
I have recently entered about 1000 products into my Virtuemart store and now I need to be able to relate the products but I need to do this slightly differently to how this other bulk related products plugin works. I need to be able to select the check boxes of the products I want related and click a button which then adds all these products that have been selected to each other (so if I select 4 products - then in each of these there will be the other 3 in related products). Does this make sense? Please see my attachment of how I see the system working.