The good news is there are already a handful of very nice ploppable skyscrapers in the workshop, after only a week. Some are very tall even compared to the landmark towers in the game, and I've been able to make a nice little CBD cluster in my city. SC4 was pretty much the same way, the default skyscrapers were pretty wimpy compared to the BATs that came along and I usually ended up plopping most of my tallest buildings anyway. The 4x4 growable limit is kind of sad but at this point who knows what might be moddable.