Different standards. HasTak has both public safety requirements and internal standards. Their standards say it can't be done with the current materials, but a third party or KO operation doesn't have those standards. I'd imagine much bigger and there's risk of the figure just collapsing long term. It takes a lot of tech to build tall things and not have them pancake. A figure is even more difficult as the entire upper body is going to exert force on your joints, especially the hips. Similar issues with downsizing. If you downsize a figure you make the parts smaller which runs you right into choking hazard restrictions. In addition key parts might not have the tensile strength when up or down sized needed. HasbTak is trying to build things that can stand up to play and that last. If Zeta Star builds a unicron and a month later it collapses, they can just fold up, get a new corporate name, and try it again later.