[Grammar] 'even if it be' or 'even if it were'?

[eeshu]

I feel quite puzzled by the following pairs:

1. We won't change our plan even if the rumour be true.
2. We won't change our plan even if the rumour were true.

1. Whatever be his defense, we cannot tolerate this disloyalty.
2. Whatever is his defense, we cannot tolerate this disloyalty.

1. Whether he be right or wrong, he'll always go his own way.
2. Whether he is right or wrong, he'll always go his own way.

1. If I were you, I would do it another way.
2. If that be so, we shall take action at once.

Could anyone please explain to me 1) if both sentences in each pair are acceptable? 2) If so, are they interchangable? 3) if not, any difference?

 

[5jj]

1. We won't change our plan even if the rumour be true. Present subjunctive (be) to show that the ‘being true’ is a hypothetical case.
2a. We won't change our plan even if the rumour were true. Not acceptable in this form.
2b. We won't change our plan even if the rumour is true. As with #1, except that the subjunctive form is not used. Some speakers consider this substandard, but it is the norm in BrE.
2c, We wouldn’t change our plan even if the rumour were true. Past subjunctive (were) to show that the being true is less likely or even not possible.


3. Whatever be his defense, we cannot tolerate this disloyalty.
4. Whatever is his defense, we cannot tolerate this disloyalty.
The explanation is the same as for #1 and #2b above. It’s more natural for ‘is’ to go after ‘defense’