(1) I will jump out from behind the couch. Then I will tell him: "I have been in the room all along."
(2) I will pronounce him dead. Then I will tell him: "You have been pronounced dead."
The above two are not of concern. I include them only so you see what utterance I'm trying to report in the following sentences. Consider, please:
(3) I will jump out from behind the couch and tell him I had been in the room all along.
(4) I will pronounce him dead and tell him he had been pronounced dead.
(5) I will jump out from behind the couch and tell him I have been in the room all along.
(6) I will pronounce him dead and tell him he has been pronounced dead.
(7) I will jump out from behind the couch and tell him I will have been in the room all along.
(8) I will pronounce him dead and tell him he will have been pronounced dead.
(3) and (4) sound most natural to me: completely grammatically correct. (English is my first language.) (5) and (6) sound like slangy versions of (3) and (4), okay for speech but not, let's say, for a high-school essay.
(7) and (8) sound completely wrong to me. Yet they look to me like the (prescriptive-grammar) grammatically correct ones. After all, the speech is taking place in the future, so you need "will have been" to report an action that, at that moment, will… have been.
So my questions are:
Are (7) and (8) actually the (prescriptive-grammar) grammatically correct ones, or are (3) and (4) (or something else)? And if (7) and (8) are (prescriptive-grammar) incorrect, why?
In case you're wondering why I used two examples, it's because the semantics are slightly different. Or so it seems to me, anyway. In (1) the being has been continuous until the time of speaking, whereas in (2) the pronouncement has occurred at a specific point in the past.