Instead of the "gas giants are too dangerous" message, it would be awesome to be able to enter and terraform them. Colonies could be placed, but they would drift around on floating platforms instead of sitting on the ground. There would be "terrain", but it's invisible (or possibly textured with animated/particle clouds?), perfectly flat, and can't be edited. Gas giants have white spice; this appears as vortices rather than geysers. By default, all gas giants are T0 or T1; thunder/firestorms are 5x more common than on normal worlds. Terraforming is possible; the lack of any surface means plants and creatures can't survive and stabilize the T-Score. There is no ecosystem, so the colonies are limited to a city hall and a few buildings.