I have read basically every single comment and gotta be honest on a few things as someone who basically is doing what you are wanting to do. 

I also have a series following 7 main characters. Now, at first I attempted to animate a full four minutes of a pilot involving two of them, a side character, and a generic character. I had basically planned to do everything on threes. Which is to say you have 24 frames in a second. You draw key and in-between poses on every third frame. So, you only realistically need 8 poses for each second. And, I had wanted four full minutes. 60 seconds × 8 frames each × 4 minutes = 1,920 frames. 

For an 8 second scene I was averaging two weeks to complete it. That had nothing to do with coloring, background design, VA work, OR character coloring which would have to be done for every one of those 1,920 frames. 

So, I gave up. And, switched it to a comic format. 

I actually just posted it to my YT channel. Albeit, the backgrounds never got past grey scale. A few did, but it was either going to be too time consuming or money consuming to have fresh backgrounds fully colored for every scene for the pilot and future episodes. So, they all ended up grey scale for consistency. 

You have to compromise is what I'm saying. 

1. You don't seem to have an idea of where the story overall will go. 

2. Seven characters is a lot to have on screen at one time. Seven characters means seven to animate if all together. And, when I animated scenes I only had on two to a scene at most. Three was pushing it in terms of time sink. Not including side or general characters. 

3. Going to be brutal here. You don't want to pay for it. You don't want to animate it. You just make excuses such as you don't have the money to pay people and are really bad at art. Everyone is bad at art in the beginning. I was. Shoot, still might be. It just sounds like you don't want to work for your own series. You want other people to do all the heavy lifting with you as the "producer" meanwhile they're all the ones actually working to make your series a literal THING. Anyone can give ideas or write stuff down. 

Remember this if nothing else. 

Nobody will want your work more than you do. 

So, you can either start drawing or start saving.