There's the kernel of an interesting idea here, but of course the original suggestion is a drastic change - much too easy to get a reset, encourages countries ganging up, etc.
Taking a step back, are we looking for a much easier way to win/reset, or are we aiming to make strat targets more useful and interesting?
A more balanced way to bring strat targets back into the game (right now they're pretty much ignored...) might be something like this:
A country wins if it
- captures 40% of all fields (or whatever the current % is); OR
- captures 39% of all fields, plus flattens BOTH enemy HQs and ALL enemy cities (HQ and all cities from each enemy country); OR
- captures 36% of all fields, plus flattens ALL enemy strat targets from both enemy countries (HQs, all cities, plus all AAA/radar/ammo/fuel factories and training facilities).
As per the zone system, if a master field is captured, the cities/factories in that zone are no longer enemy cities/factories.
This way the reset might come slightly easier, but not a lot; and if you need to get both HQs and all cities, there's no huge incentive for two countries to gang up; and strat targets become useful and interesting again.
The actual percentages would need to be carefully chosen to get the game balance right... just off-the-top-of-the-head guesses above.