This is what the tools industry really needs: a standardized form factor for LI batteries so you can mix and match different brands. Of course we all know why companies are reluctant to do this.
I agree with you and took matters into my own hands. There are several threads on DIY adapters. This one is Ridgid to Dewalt, but I am also going to build Ridgid to Ryobi for my new hedge trimmer.
I've always said that ISO needs to release a standard battery connection for Lithium Ion tools. even if the Mfr's created an ISO adapter. It would make standardization easier, it would also allow for competition where a plant, shop, factory, whatever can shop around and not be married to one platform.