The good news is that there is functionally no difference in the product you'll get if you book a Business Everyday award vs a Business Saver award. The only difference is in availability - there is less saver space available.
If you see a Business Saver award available on the route you want - book it!
A downgrade is very unlikely, and would be covered by downgrade compensation. Once you have a ticketed reservation, you're good to go.