No, i still think tanks at 6 will not be used all that much. The only reason tanks are purchased in AA50 are
A) Speed
B) Build Caps
Germany builds tanks because they can build 10 units, why not tanks. Japan builds tanks because of, once again alot of income and small number of units that can be built. With 6 IPC tanks you would be nuts to buy them over mech inf, imho, esp if art matches up with them. The only redeeming quality of tanks would be the strat bombers attacking at a 4, but once again, strat bombers at 11 are junk, for 1 more you get a bomber with 2 more range. Sure it cannot defend well, but that is what a fighter, costing 10, is for.
I just ran the numbers in TripleA battle calc (I know not the best).
6 inf + 1 bomber can kill 6 inf 62% of the time
4 arm + 1 bomber can kill 6 inf …62% of the time
Same cost, same offensive effect, but mech inf are so much better on D its not even funny. And you will almost always have air attacking with you, unless AA guns go down to 4 or something.
Mech inf: 1/2/2 @ 4 ipc
Arm: 3/3/2 @ 5 ipc
H Arm: 3/4/2 @9 ipc (is 2 hit)
That is the only way I can see using each of those units.