[Fyron]

You can use negative values for "improves planetary value" ability, but I do not believe negative system bonuses function. Also, planetary bonuses stack (add all of them that affect the planet together, including negatives), and system bonuses do not stack. You have the same affect with the happiness abilities: system happiness is positive only and one per system, planetary happiness can be negative and you can have as many as you would like to use.

The hyperdrive motivator is probably an emergency movement device, right? Such devices require the presence of a space yard in the sector to be repaired. So, giving it a 0 SY ability means it can be repaired, thus used once per turn. Personally, I would remove such devices because they are a huge hassle to use in PBW games. You have to remove all of the ships from the fleet and give them use component orders one by one...

Another possibility for the cloaking device having an engine ability is that it can now be targeted by anti-engine components. I recall much discussion over just how to implement ion blasters or whatever they are that just damages electronic systems.