For most people, two-a-days aren’t necessary to get faster. But I understand from a pratical perspective where this might have a place! With that said, Adaptive Training will still take into account any additional work you do beyond your scheduled workout.
If someone was beginning to incoporate two-a -days for practical reasons, I would suggest doing exactly what you are doing and make one of those a structured Workout and the other an easy endurance ride! 
This also seems like an effecive alternative option to ensure maximum quality, but as you mentioned already, consistency trumps a perfect plan that you don’t adhere to!
Sounds like you have made a plan that works for you though, @JoeX! Hope it all goes well!