I don't have any help for you. As I've learned as I've gotten older and done more projects, solder sucks, crimps are better, quality crimps with a matching plier and terminal system are better yet...but my path to get there did not include reading it in instructions with a product I've purchase.
You might provide the correct butt splices with instructions to purchase or borrow the correct pliers. Include instructions on how and why to do it the way you recommend, and put in BIG BOLD LETTERS that unless the instructions are followed, caveat emptor. I know that isn't your style though...and I don't really know how to get you where you can provide the 100% solution that you can fully back.