I see; even as the creator of this mod, I'd recommend to "do" instead of "plan" for this one, for what I'd say are reasons similar to spoilers. By an "actual" Platform I was wondering if you meant only that you could place an engine on the tiles in the sandbox, or whether it would be a new Space Platform with all the mechanics: automatic building, platform tiles, asteroids, and so on.
I haven't completed Space Age yet, but I'm sure that we'll encounter more entities that have requirements about pressure and gravity; for example you cannot place roboports in space for the opposite reasons as the engine, and that means if you can place engines in the sandbox, you cannot place roboports. I'll have to think through exactly how/when those properties should be adjustable. But, I don't think there's a good way to have an "actual" Space Platform, because it means you can "cheat" by interacting with the rest of the universe.