When Vigilant Elector's action is triggered and he is counted as an attachment :

Does he gain only the Attachment subtype and mechanism (sacrificied when its attached thing is destroyed, rb p.7) ?

Or does he also gain the Support type ?

If he does, does he lose its Character type ? In Cthulhu LCG, no, as far as we can tell with the FAQ, a permanent can be both. There is no mention of it in Warhammer: Invasion so I'd say a permanent can be both.

I, for one, think he remains a Character type card and does not gain the Support type: Rulebook p. 7 mentions that "often Attachments are Support cards".. Thus some Attachments are not Support Cards. ;-)

It has/will have errata to say that it counts as a support card so you can target it with Pillage, Demolition etc. Link

Keep in mind in if that errata doesn't officially happen before the regionals it still counts as a unit while its attached and can be targeted by a whole bunch of things to get rid of it before it kills the thing its attached too.

Okay, thanks for the link.

So, post-errata, it will count as a Support and it won't count as a Character anymore. I hope this last part will also be clear in the errata.