This is exactly what I try to do and what I've seen successful systems do. Laying out adjacent markets, potential pivots, likely product features, etc. is a we

This is exactly what I try to do and what I've seen successful systems do. Laying out adjacent markets, potential pivots, likely product features, etc. is a weekend-long exercise. That can help define both where the architecture needs to be flexible, and just as importantly, *where it does not*. Over-engineering happens when you plan / architect for things which are unlikely to happen.