Your assuming that the attacker with a range advantage can only be attacked by his target. If an ally to the target manages to close and get in range, the tables can turn.
If they can manage.
I feel like you have come up with some good ideas to prevent people from abusing the House Rule. But, I think, what people are trying to point out, is it can be abused - fairly easily.
If you make it a bit more restrictive (the same way Full Defense is restrictive), it is less likely to be abused.
Let's say a character with
Guns 5 (weapon 4 assault rifle); Athletics 5
Supernatural Speed
Dodge stunt
wings
4 refresh and they are dodging at +8 and can fly. For free they can move 2 zones as a supplemental. Given enough zones to maneuver, they can rarely be engaged. They still dodge at +5 or 6 and fire a weapon 6 assault rifle from 3 zones away.
If the enemy chooses to go full defense, the gun-wielder moves 2 zones away and does a navel gazing maneuver.
Not that every scenario would end up like this...but when it does, using regular attacks is sub-optimal. Just make sure that many scenarios has ranged enemies, or close quarters.
***
Or
Supernatural Toughness
Supernatural recovery
Catch +3
Good Athletics (or Footwork)
Great sword: weapon 3 or higher, if it's an IoP or something.
This guy is more expensive, refresh-wise(-6), but doesn't really care if he gets hit for a couple extra stress.
These are two characters where it makes no sense NOT to use full Offense. There are probably other situations/builds where this is true.
It's very rare to build a character where it makes no sense not to use Full Defense. Reflect Attack custom power would be the only thing I can think of. And that's a very expensive build to make it worth while...like, 10+ refresh.