... How about 5 points, and the Phantom cannot be targeted at Range 3. Simple to word, simple to use, and not too outrageously effective since Range 3 shots are fairly ineffective anyway. For ECM, maybe have the opponent roll an attack die when he attempts to TL the Phantom, and he succeeds on hits/crits. That would have the advantage of using a pre-existing mechanism for simplicities sake but would still perform a logical function. Self-Destruct looks just fine to me exactly as you wrote it. Since it is a sensor upgrade that is only available to relatively expensive ships (and uses up that valuable slot), plus it requires an action, I don't think it is out of balance at all.
Simple is sometimes better, you mean? Well i guess your are right in this point - X-Wing players are not neccessarily hardcore strategy players, so how about this: you cant be attacked at range 3 and you gain +1 defence. If you get hit, the cloak will be disengaged (just like the existing stealth device) but you can activate it again next round.
ECM sounds good to me - why don't include a dice? Ppl love this.
For self-destruct i don't wanted to create some sort of TIE Kamikaze squads - so system upgrade only
Thanks for your feedback