I understand your concerns.
But if you're looking to use the application professionally, version 7.x is going to be a long way from the interface and user experience of the current version. You are also likely to run into problems with PDF creation, and won't have any options for digital publishing other than PDF.
Currently, the subscription (annual) is $29.99/month and would get you any upgrades that come along during that year.
I've also been told that you can cancel your subscription plan. It turns out to be true but you will get charged for 1/2 the remaining term when you cancel. At least that's what happened when I tried to cancel an Illustrator+Stock subscription I no longer require.
Thank you "Tech Comm Tools".
I did not think about the interface, also the potential problems.
You and everyone else have been very helpful.
That pretty well eliminates 7.0 and the probable wasted time.
The charge for 1/2 the remaining term if I cancel a subscription is also something to think about.
Now the remaining question is the availability of FrameMaker 2018. I doubt Adobe will announce anything before it's time.
Back to the "drawing board".