Bearbricks are transforming, and so are the Sentinel pens... so there is now precedent of licenses being issued to 3rd parties to produce and sell converting Transformers (as of last year). It's just very hard to design and produce converting toys, and then have to go through all the hefty added expenses of safety testing, trademarks/patents, and licensing (something that the unlicensed people don't have to spend money on), so probably no one in the past has been able to do it before on a major scale.