Hi.. I'd love this to be able to set that a filled container can be shot up with a rocket to a space ship.

Looks like this will mess with weight. Items in container are condensed using stack size, but stack size is not relevant for their weight in rocket, they are separate properties.
I thought about how to make containers rocket-loadable. My points:
1. Stack size is measure of items "bulkiness"?, rocket load value is weight.
2. To load containers in rocket they must preserve weight.
So, maybe containerisation should be made by weight rather than by stack size? Could be like 1 container - 1 rocket.

I'll be keeping containerisation by stack size rather than weight because the primary purpose is to help with density in trains and belts. Factorio's 'weight' isn't really weight at all, it is just arbitrary numbers created for rocket silos specifically for a particular intended balance of rocket logistics.

Containerised items should just inherit the weight of whatever was put in them, plus the weight of the container themselves. That way, you get no advantage from containerising items before launching them in rockets (although, depending on how you configured this mod, you may be able to fit more items in the space platform hub if they're containerised). I'm not sure if the current version of the mod sets the weights correctly. If not, then I'll fix that in the next version, whenever that is (probably coinciding with Freight Forwarding for 2.0).