One issue to consider with the pay to export later model is that it's almost impossible to develop a game without an export to test on devices, and people you want to get input from.
As a service you wouldn't need to export all the time, so I agree that other plans than yearly would be beneficial.
Six months, and even quarterly might be good.
Edit:
On the other hand we still don't know exactly what the subscription would offer.
Give me web hosting with that, and I would likely poop my pants to get in line to pay.