I have a question.
Present tense. Right now I have a question.
I have had a question
Perfect tense. At one point, I had a question. It may or may not be true that I still have it now (might be made clear from the rest of the sentence).
I had had a question.
Pluperfect. At one point it was true that at an earlier point it was true, that I had a question. "I had had a question for some time, but I never got a chance to ask it".
Now, in each of these the verb have is used once in the sense of "to possess" or "to hold" and in each of the second two it is used as an auxiliary to modify that other have.
You propose.
?I have had had a question.
Which we would presumably have to interpret as some sort of super-perfect stating that at some point it was true that at an earlier point it was true that at an earlier point it was true, that you had a question. It's not clear what you are saying about the current state.
As such, you've just created a non-standard variant of either the perfect or the pluperfect, but you leave us confused as to which - and imply that you are confused about the matter yourself.
You suggest it might be better as:
?Having had had a question, I asked it.
But this presumably would mean that it being true that at one point it was true that at one point you had a question. Again, it's not clear just what this is supposed to mean, and one possible interpretation has this as impossible (because one way of untying the knots leaves us with the suggestion that you no longer had a question at the time you said it).
In all, this reminds me of some comic nonsense writing that has been done - sometimes well - but were the whole point of it is that it was not good English. Barring that goal, none of this makes any sense.
You talk about "unique time travel situations", and I could see someone deliberately engaging in this sort of abuse of auxiliaries to describe that. Still, the implication is "this time travel has so messed with the logic of causality that English grammar can no longer work to express the resultant mess". Once you're doing that then you've deliberately thrown the rules of grammar away for effect anyway, so asking if it's grammatical is not just besides the point, but counter to it.
Really though, this is not grammatical English. Nor is it a useful construct to anyone who perceives time and causality as being related things.
You're using the conditional perfect tense here, so an acceptable form of words is:
... (my fault, [I] didn't really know how time consuming it would be).
Note
You should leave out the word much. Time consuming is an adjectival phrase describing it; it is not quantifiable, and therefore much is inappropriate.
However, you could also write
... (my fault, [I] didn't really know how much time it would consume).
and it would be equally correct and convey the same meaning to the reader.
Best Answer
I don't think your idea can exist.
In your sentence...
... the conditional
ifand past-tense makes your openingcanillogical.Instead,
-or-
-or-
If you're writing fiction, and the idea you're trying to communicate is that you could be doing something else right now if you could change the timeline, I would say it like this:
When you try to say "I can have had been" you're creating a time paradox. Consider the following:
If the above is true, why aren't you reading? And if you were reading, you couldn't be sending yourself a letter to tell yourself to read, so you wouldn't be reading.
So, like I said, I don't think the idea (as you've expressed it) is able to exist, the grammatical problem merely uncovers the time paradox.