I have a feeling that this may be the dreaded (at least for me) subjunctive. But I'm really hoping it can be analyzed as the imperative instead. I am hoping I can use this expression to help explain a similar pattern in Japanese.
Can we understand "Be that as it may" as meaning the same thing as "Let that be as it may, and yet still..."
EDIT: Thank you for the replies. I realize I made a mistake in my analysis of my reformulation above. Even if "let" is taken as the imperative, that wouldn't extend to "be."
I did a little more searching, and in its discussion of the subjunctive, Wikipedia gives examples such as "Be they friend or foe" and "Come what may," which both seem very similar to "Be that as it may."
Also, if I understand correctly, the "be" in a sentence like "May the force be with you" is the subjunctive. I think this sentence is very similar to my reformulation above ("Let it be..."). So it looks like even my (undoubtedly liberty-taking) reformulation uses the subjunctive.
All of this leads me to me to suspect that the "be" in "Be that as it may" really is the subjunctive. I would welcome any other thoughts, corrections, or input.