[Mayday]

Some other things:
Technologies that require multiple prerequisite techs.
Sensors for mines. These should be expensive additions to the mine, and only work on the sector the mines are in.
Also, higher sector limits on mines. Or at the very least adjustable ones.

It might also be nice to have a Terraformer ship type, which acts like a colonisation vessel, in that it is entirely consumed after use. To go on this design alone should be Atmospheric Modifier Plant and Climate control facility components that, that, when ordered to 'colonise' or whatever, are changed to be planetary facilities. By making the ship a small one, you can limit the number of facility components it can hold to 1, so there'll never be a problem when there aren't enough facility slots on the planet for the terraformer to fill. Also, I feel that this would indeed be balanced, if the facility component is the same cost as the facility itself. This is because you have to build it one the ship, and so have to pay for the other components too, and the maintenance while it is in transit, and the entire ship is consumed on use, so there's no 'repair and do it again' method, like how I build my Quantum reactor Planet Builders and Warp point openers and closers.

Anyway, this has the result of being a faster way to build this facility on all needy worlds in the empire, since a high population world can build faster, and will easily produce it in less time than the colony would be able to.
Possibly, you could make it so that the 'unpacked' facility was a different one altogether with a slower terraform ability than the planet built one, only 'buildable' by being unpacked. Although I would say that the cost of having the major production centres' shipyards focussed on building terraformers instead of warships should be tradeoff enough.