The theory behind my strategy is as follows:
1) In order to be the "first application" according to 4(B) and 4(C) an application presumably must be a "duly filed application" according to 4(A)(1).
2) The definition of a "duly filed application" is found in 4(A)(2) and 4(A)(3).
3) By default, App 1 is the first application for X, because it is duly filed, even if it is abandoned, and regardless of when it is abandoned according to 4(A)(3). By default App 2 is the first application for Y.
4) If some future authority in some foreign country determines that, under 4(A)(3) U.S. law would have retroactively cancelled the "duly filed" status of App1 because of abandonment for non-payment of filing fees, then App 1, not having been duly filed, cannot be the "first application" under 4(C). App 2 becomes the first application for X and Y.
5) Even if a foriegn authority found that App1 was not duly filed, but was still the "first application," that finding still would not defeat the priority claim to App 2 for X and Y according to the OP.
This, I think, is where we got hung up. Nearly all discussions regarding Article 4 revolve around 4(C)(4) and the 1 year limit of 4(C)(1).
Although the OP had nothing to do with time limits, the questioner (myself) reflexively presumed that 4(C)(4) would insert itself into the problem.
But the language of 4(C)(4), in its convoluted manner, seems to state in its preamble that it is to be read as a definition of "first application" only for determining the length of the priority year.
And article 4(F) allows priority claims to multiple documents within the same PCT app and subsequently at the national stage.
So long as the PCT app claiming priority is filed prior to the anniversary of App 1, it is immaterial how, when, or if App 1 is abandoned. Nothing in Article 4 prevents a priority claim to App 2 for X or Y.
In the immortal words of Bill Murray: "It just doesn't matter."
It seems I got worked up over nothing (unless someone finds a new flaw in my analysis)