Tbh, there's also a butt-tonne of luck. With this game, if anybody had had permanent IRL stuff to deal with and had to drop out permanently, we'd probably manage to recover, but the dynamic would be totally different. If I hadn't previously played with any one of you, there would be a complete wild-card in the group, which in larger games which can more easily accept a drop-out is fine, but in this wouldn't be. Essentially, a GM is only as good as their players allow them to be - and vice versa.

Something to think about is whether you as the GM want to participate in the plot personally. In this, 'my' characters are very much plot devices/NPC's, in the sense that, while one or more of them may or may not play a directly antagonistic role, they also facilitate whatever personal exposition you guys want to achieve.

I also recommend, when asking players what they want, especially if you don't know them well personally, is to primarily give them two or three options and invite suggestions as an extra. It stops players from being cowed by having to take responsibility for a bad idea, because all they have to do is lend support to their preference.

What've you got in mind, anyway?