[Alneyan]

1) The purpose of this thing is to help you keep more movement when your vehicle control components are being destroyed. Problem is, if you start losing bridges and the like, your ship is virtually dead, with destroyed engines, no defence left and few weapons remaining (if any at all).

2) Scanner Jammers counter Long-Range Scanning, and not claoking (they do not allow cloaking either). Scanner Jammers are however almost obsolete because the Scattering Armour offers the same ability, plus a +15% bonus to defence. Their only use is to have the ability within your ship rather than on the more vulnerable armour (armour might be destroyed in skirmished or even by wormholes).

I have only one example where it would have been somewhat important. In a 2vs2 game, Parabolize had sent warships behind our lines, and a couple of these had lost their Scattering Armour while running through a minefield or two and/or a blockade. It allowed the Crafty Ones (Slynky and myself) to scan one such vessel, which taught us the vessels in question had barely any supply left. If Parabolize had used the Scanner Jammer instead, we would have been unable to get this information. Does that warrant the use of the Scanner Jammer? I would say it doesn't if you are already using the Scattering Armour for its defensive bonus.

3) The highest level of Shield Regenerator is worth it if you expect your ship to Last for more than seven turns (or so; I do not recall the exact figure) once its shields have been damaged. Otherwise adding one more shield generator makes more sense. I believe it may be worth it when the odds to hit are very low (but if you are fighting in such circumstances, you should have another more crucial edge).

Shield Regenerators are also helpful to keep these boarders at bay, if you have been attacked by Shield Depleters. This is assuming the actual boarding ships do not have Shield Depleters of their own, and are relying on another vessel/ship to deplete shields. (Such strategies can be made to work, but unreliable, and more of an emergency remedy than a sound scheme)

And if you are really concerned of losing your ships, a Self Destruct Device and/or a Security Station or two will do the trick as well. A single Security Station V is enough to repel two Boarding Parties V, and two of them should be enough to make you safe from most "expendable" boarding vessels (Escorts, Frigates and the like, which are often used to trigger your Self Destruct Devices rather than for actual capture attempts). Likewise, a Self Destruct Device should do the trick against more "specialised" boarding vessels (Shield Depleters, many Boarding Parties and so on; these would actually try to capture your ships).