[…] and therefore, whoever could find out a fair, cheap, and easy method of making these children sound and useful members of the commonwealth would deserve so well of the public as to have his statue set up for a preserver of the nation. (2)
Swift is mocking the British approach to public policy, which emphasizes economy first. Absolutely everything has to serve a purpose.
As to my own part, having turned my thoughts for many years upon this imports subject and maturely weighted the several schemes of other projectors, I have always found them grossly mistaken in their computations. (4)
This is the cue for the narrator to start throwing out wild estimates of the number of people in Ireland.
The question therefore is how this number shall be reared and provided for, which, as I have already said, under the present state of affairs is utterly impossible by the methods hitherto proposed. (7)
So far, the narrator hasn't actually stated which methods have failed. There's a lot of political posturing going on, which Swift knows is essential for any kind of political tract—satirical or not.
The Proposer (Narrator)
After all, I am not so violently bent upon my own opinion as to reject any offer, proposed by wise men, which shall be found equally innocent, cheap, easy, and effectual. (31)
In other words, wise men aren't so easy to come by.
Therefore, let no man talk to me of other expedients: […] of being a little cautious not to sell our country and consciences for nothing. (28)
Swift not only provides his own (true) suggestions for improving Ireland, but scolds political mercenaries without principles.
But as to myself, having been wearied out for many years with offering vain, idle, visionary thoughts, and at length utterly despairing of success, I fortunately fell upon this proposal, which, as it is wholly new, so it hath something solid and real. (30)
Swift isn't just upset by political greed. He wants to start a discussion about solutions.
But before something of that kind shall be advanced in contradiction of that scheme, and offering a better, I desire the author or authors will be pleased maturely to consider two points. (31)
If there's anything Swift liked, it was a good political argument. He heads his opponents off at the pass by anticipating their counterpoints.
I grant this food will be somewhat dear, and therefore very proper for the landlords, who, as they have already devoured most of the parents, seem to have the best title for the children. (12)
Swift hated the idea of political greed. Many of his political arguments were actually moral ones, arguing for charity toward the Irish.
I desire those politicians who dislike my overture, and perhaps be so bold to attempt an answer, that they will first ask the parents of these mortals. (34)
Swift loved to be one step ahead at all times. He wrote Verses on the Death of Dr. Swift, a poem anticipating public reaction to his death, in 1739.
Sixthly, this would be a great inducement to marriage, which all wise nations have either encouraged by rewards or enforced by laws and penalties. (25)
In Swift's dystopian Ireland, even marriage is viewed as a means of producing goods for sale. Chilling.