Ben,
I'm delighted you find this upgrade idea interesting. Six months ago, I proposed this idea to Air France management. I also suggested another idea, not advantageous for customers, but profitable for the company. This involved selling upgrades to 1F seats on A350s and similar seats, which were previously free for Platinum members. These seats offer a significant advantage over other business class seats.
Since Hyatt offers a bonus every 10 nights, I thought we could do the same for airlines, and they listened. As you mentioned, going from 300 to 900 Ultimate Pass Points (UXP) is a long journey. Setting intermediate goals motivates customers to progress, to fly more to earn a reward.
My next step is this: The number of Ultimate customers is not very high yet, but the next step is to encourage them to accumulate well beyond 900 UXP in order to benefit from additional advantages, beyond simply carrying over points to the following year.
Regards