What, did you think we were done? Foolishness! We haven't broached the subject of vehicles, except to address them as particular units. Specifically I have issues with vehicle BS and upgrades.
I have a real problem with the standard ballistic skill of Eldar vehicles being a puny 3. Sure, their vehicles are manned by grocery clerks and accountants, but they are clerks and accountants who are hundreds of years old! Oh and where's all that supreme psycho-reactive technology we all read about in Path of the Warrior and other myriad publications?
In general I would like the base vehicle BS of Eldar vehicles to be higher. Either it should be increased to BS 4 OR it should be handled as an upgrade option (see Spirit Stones below).
I mentioned earlier that spirit stones are constructs which hold the spirits of dead Eldar. These Eldar are sometimes mounted into wraith units to serve as additional troops, but more often than not they are attached to vehicles, to help maneuver the vehicle when the crew is stunned or otherwise occupied.
In the current rules, they are the equivalent of the Extra Armor upgrade from the Imperial codices.
I'd like to see this ability moved to a separate upgrade and Spirit Stones become... Power of the Machine Spirit! In fact I would like to see this upgrade increase the BS of the vehicle by 1 and/or allow the vehicle to take an extra shot (at BS 3 or 4).
No changes needed, I believe. They are rock solid as is.
While I am paranoid about my transports crashing and disgorging my mangled units into the burning wreckage, I am not stupid! Twenty points is way too much to spend for this upgrade. Try 10.
Holo fields are almost too good as they are. I don't see any need to alter these unless - going back to my Spirit Stones changes above - the Eldar actually get the PotMS upgrade. In that case, I could see reducing the cost of Holo fields and making them do what Spirit Stones do now. That way you keep the "glass hammer" aspect of the Eldar in all their default-AV-12-glory and bring the focus back to their ability to lay down withering fire.
Wave Serpent Energy Field
I don't see any reason to change this. It's a good all-around ability.