This would be a great compromise, but I suspect that part of moving to the subscription model would be to do away with "one major version release per year" entirely and put out more frequent releases.

It's a tough position for Jetbrains. I've got a lot of sympathy, the annual release + purchase model is very limiting - but changing to a subscription model comes with its own problems that you can't just brush under the rug by offering a promotional price and talking about flexibility.