In Early Modern English, the second person plural (singular) declensions were:
Nominative: - Ye (Thou)
Oblique: - You (Thee)
Genitive: Your (Thy & Thine) & Yours' (Thine)
In Language there are exceptions to rules, or what-have-you, but it is to my understanding that "Be ye" is subjunctive, not imperative, unless it is a different form of subjunctive. Obviously in English Bēon was the original infinitive which evolved into "be," before the north received "Earon" from Latin, however the North readopted "be" for subjunctive. In my thinking, "Be ye" and "Be thou" would mean the same thing: subjunctive, e.g.:
"Be ye good and good should come/be thou good and good should come" would both be the same as saying "If thou beest good, good should come --" it may not, but it is an obligatory return vs. all saying: "Be you good and good should come/Be thee good and good should come --" it may not, but it is not an obligatory return regardless of how you act.
Obviously this is not the best example for subjunctive, but my question is clear -- one is imperative and one is saying if you choose to act a way then "x" will happen...