I strongly disagree with this comment (needing an MVP). For a serious B2B product you need a team, sales process and social proof/track record that convinces the customer you will deliver on your promises.

But above all, you need a product which solves a tangible, significant problem for the customer!

If the willingness of a customer to sign a prelaunch sales agreement comes down to the quality of your MVP, something has gone wrong in your sales process and the customer is just looking for an excuse to decline.