This is a great idea, but you have to be very careful with something like this. An open-ended universe allows for more ideas and story arcs in a roleplay, however, it can also be confusing or unorganized. The main problem is that a roleplay like this can make it easy to have too much going on. In order to pull it off, you need larger events happening one at a time, along with the regular character interaction and conflict a roleplay usually includes.
If you are not confident in your idea, you should wait until you have more experience and can better develope your idea before you start. But if you think you can make a great roleplay, I encourage you to do so.