Can we get a list of who are companions are, please? I've got the general idea, but it's been a long time for most of them.
I don't think we should bring many.. they're not immune, and this is really effing dangerous. Army would definately be a pinwork army of undead kind of thing, with maybe a few mercenaries to help relay orders and provide some brainpower along the trip. We might need to build a bridge or some battering rams. And we can alter undead to toughen them up and provide natural weapons.. claws, spiked arms, etc, but I don't think we could provide ranged attacks that way, so we'll want a bowyer and a fletcher. Maybe five or six mercenaries, preferably non-human ones, mostly to relay orders and let us have some skeleton bowmen.
If we can get safety gear for us and one other, though, we should bring someone, so we can show this isn't a monsters-only expedition. It would also be nice to have someone keeping Sydney human, that is, giving her someone to talk to, and dragging her back after we do something nasty to gain power.
Also, I don't see why we'd abandon anyone if we leave. We can send messages and exchange small items via bird, and we'll likely take at least a slightly meandering path to raise an army, so if someone has to, they can catch up.
Anyway, step one is to get some support. We should try to work on both the powerful people and the general population. When we leave, there will be people back here working on the cure, in addition to some of our own people. If the population supports them, they will do much better, particularly if we fail. Besides, isn't that what Sydney enjoys doing? There will be dark days ahead, and having a happy memory to draw on, and knowledge of what you left behind, should help.
..plus, there might be physical advantages as well as psychological ones if we can get thousands of people here supporting us from afar. There is the freaky drider-worship thing, and I think Queen Alexia literally got strengthened from that effect following the fight club incident. She had a hand she wasn't supposed to have, for one, and that robe she was wearing was way too big for normal Sydney.