I find some of my favorite books are the ones that take something fairly straightforward and do it really well. If you have a great hook and the book takes me step by step through it, right in the action, that's great. If it gets off on a bunch of side tracks, that can be frustrating.
If it was me, I would pick the most important things, get a basic outline where you can see through to the end and start writing. If along the way you pick up a few subplots and change things, great. The manuscript can be reedited at any time, but it will probably help to get some sort of framework down in the first draft. A lot of those "Oh, wow, cool!" ideas may sound great in your head, but once you try to write them down, you may realize they don't fit these characters, or would be better saved for another manuscript. Or, once you reach the end, you can always bulk up places that need it.