You can make it a team effort to come up with the ideas, or even start with the problems you are trying to solve. I’m not clear on if you are purely looking at

You can make it a team effort to come up with the ideas, or even start with the problems you are trying to solve. I’m not clear on if you are purely looking at architecture or also product features, etc. Your strategy would need to fit into all of that too. The plan is long term so it’s ok to take some time over it. Ask lots of questions to different stake holders to get a good picture of the problem you are trying to solve.