yea, a SV-51 might just topple that thing. Looks a little flimsy. The other thing is that I'm pretty sure that even a 1/60 yammie, if balanced, will be too large to position on a lower tier, because it'll obstruct the columns around it.
However, if its cheap enough, I'd want to put a 1/60 version of each plane on the mounting arm and its respective GNU battroid underneath.
Also, they really shoulda sold something like this with their GNUs... having a figure without a stand to pose it on is kinda dumb. I didn't mind them cutting out super packs as much as that.