I think the passage in question, MMK 7:3 is a bit more straight-forward than you're interpretation of it seems to imply (an odd sentence to write!). Essentially, all that is at stake here is an infinite regress.
Birth (utpāda / skye), abiding (sthiti / gnas), and perishing (vyaya / 'jig) are the characteristics typically ascribed by Mahayana Buddhism to compounded or conditioned things (saṃskṛta / 'dus byas).
The guiding question of the first part of this parīkṣā seems to be: are the characteristics of conditioned things themselves conditioned? And if not, how are they to be explained.
Thus, at MMK 7:1, Nagarjuna states: "If birth were compounded, it would possess the three characteristics [of a compound]." Assuming birth (and, we might add, the other characteristics) is a compound seems patently absurd, for then this characteristics would be characterised by themselves (i.e., to explain birth, one would have to refer to birth). But then, this raises precisely the problem that Nagarjuna goes on to pose "If birth were uncompounded, how would it be a characteristic of a compound?"
One obvious way out, is to argue that the three characteristics might not need to act as one, so, for example, we might be able to explain birth in terms of abiding or perishing. Hence, at 7:2, Nagarjuna cuts off this possibility by stating: "The three such as birth cannot individually be that which characterises compounds."
If the characteristics of compounded cannot themselves be compounds and if the characteristics cannot be used to determine one another, then a third possibility opens up: that these characteristics (birth, abiding , and perishing) are themselves the product of other, yet more basic characteristics. This is the thought that 7:3 gives an answer to: if we are to posit that the characteristics of compounds are themselves compounds of yet more basic characteristics, where does this cycle end?
Your interpretation of 7:3 seems to import a range of concepts I find troubling. First, you seem to reify the "this," a term that does not exist in the Tibetan. Thus, for example, Garfield, also working from the Tibetan texts, translates MMK 7:3 as:
If arising, abiding, and ceasing
Have characteristics other than those of the produced,
There would be an infinite regress.
"This" in Batchelor's translation is merely a shorthand for "this argument" or "this way of thinking."
Second, you seem to create a distinction between internal time and some sort of external time that does not sound like anything I'm familiar with in Nagarjuna---although I can see where it makes sense in the Western philosophical tradition (so Bergson and Husserl make similar divisions of time).
Third, the phrase "constituted by the transcendental ego" is far too Kantian to properly belong to this context, and I have no idea how one could reconcile the idea of a transcendental ego with anātman.
Fourth, note that it would seem more accurate to say that time simpliciter---that is, in both its "internal" and "external" aspects---is a conceptual construction (see, e.g. MMK 19). Note, however, that it is important to realise that they fact that things are "conceptual constructions" does not make them false. They are, rather, empty.
