I'm very much on the start Mac week 1 bandwagon. The rookie contract is just too important to waste. And the first year is generally a learning experience anyway. Something probably will happen at some point to open the door for Mac, but what is it doesn't? Should we be prepared for the possibility he sits all year? I'm not. BB shouldn't allow the possibility to exist either.
We also need to remember as a general rule. A QBs first year of playing in the NFL and going into the playoffs almost always ends in a loss, even for the best ones. The difference here may well be between a 3 year to 4 year championship window. That is a 33% difference, which is huge.