The ESP Guitar Company

no afaik, dont see how that would work.

The sustainer replaces the neck pickup, as in fully replaces it. There is a sustainer (I don't know if its fernandes or sustainiac) which acts as a neck pickup as well, but I don't think its a particularly good one. You can get a mounting plate with the Sustainiac which is humbucker size, and on that you can put the sustainiac and a singe-coil-size humbucker next to each other.

the pickup built into the sustainers with pickups is passive, so you don't want that,
but as someone said they make a sustainer that only takes up half the space of humbucker, leaving a single-coil slot open for what you want,
so i'd get an EMG single coil pickup in your case,

it won't be exactly the same sound you have now, but it would be the closest and easiet overall to get installed.

none of this sounds easy to install imo, expect either a difficult project on your hands, or to pay a good chunk to a tech to do it for you.

i dont think its worth 300 bucks

You could just get an ebow...

Are you guys sure two single coils will fit together under one humbucker sized pickup ring? All of the single coil pickups I have dealt with have some extra part sticking out to the sides, that you don't see because it's always under the pickguard or mounting plate. I imagine that would prevent you from having two of them side by side so that they'd look like a humbucker.

The sustainer doesn't have that triangular piece, so you can squeeze one behind it no problem. Kerry King and Steve Vai did it. They also have world-class techs to make it work, though.

^^ I think that triangular piece of plastic is why they reccommend single-size humbuckers...I assume they don't have this plastic triangle?

Some of them do. EMGs don't, the sustainers don't (obviously), the new duncans don't, the old duncans do.