Alethia and others, the NWT is not alone is saying "first" or "starting" (or an expression with a similar meaning) in Jeremiah 25:29. For example, Jeremiah 25:29 (Revised English Bible) says "I shall first punish the city which bears my name; do you think that you can be exempt? No, you will not be exempt, for I am summoning a sword against all the inhabitants of the earth. This is the word of the LORD of Hosts."The Revised English Bible (REB) is a revision of the New English Bible (NEB). The rendering of the NEW Bible is one which the WT (including Fred Franz?) a number of times liked in a number of Bible verses and it might have influenced the WT interpretation of some verses (or reassured them of their interpretation [for example, the WT used the 1970 NEB wording of the latter part of John 1:1 to support the NWT wording of "a god"]).
Regarding the meaning of "all the inhabitants" the commentary in the Oxford Study Bible: Revised English Bible with the Apocrypha says the following. "City which bears my name: Jerusalem. All the inhabitants of the earth is an apocalyptic phrase; see following note. 30-38: This whole passage has the flavor of the flavor of apocalypse, the prediction of a violent intervention of God into human history for judgment." I think the commentary is implying that some of the prophecy did not come true literally, by saying "All the inhabitants of the earth is an apocalyptic phrase", and is thus trying to downplay taking seriously that part of the prophecy.
Jeremiah 25:29 (New Revised Standard Version) says "See, I am beginning to bring disaster on the city that is called by my name, and how can you possibly avoid punishment? You shall not go unpunished, for I am summoning sword against all of the inhabitants of the earth, says the LORD of hosts." Even the ESV (which Alethia quoted) says "begin". Even the 1995 NASB (a very literal translation) at Jeremiah 25:29 says "... I am beginning to work calamity in this city ...". The Byington translation at Jeremiah 25:29 says "... I am beginning with the city ...". Likewise even the Revised Version (RV) Bible of 1885 at Jeremiah 25:29 says "... I begin to work evil at the city ...".
Jeremiah 25:29 provides context to interpreting Jeremiah 25:18 as to which city or nation the book of Jeremiah says will receive judgment first, and thus it supports the NWT (2013) saying "starting" at Jeremiah 25:18, and thus I must admit it strongly supports the claims and exegesis of the Bible by scholar (from a biblical text perspective if not a secular perspective) in this aspect. It should be noted however that the NWT of 1984 (a more literal translation than the NWT of 2013) does not say "starting' at Jeremiah 25:18 though it does say "starting off" at Jeremiah 25:29.
The Abingdon Bible Commentary (1929) [which is one of the
main non-WT commentaries which I use because it impresses me greatly] on
page 694 says regarding Jeremiah chapter 25 "... Jehovah is about to
bring all the families of the North (v. 9, cf. 1:14) against Jerusalem first, but also against all of the nations around it."
I remember that when I was an active JW the WT published more than once the idea that the Bible reveals that Jehovah brings his judgements and punishments first upon his own guilty people and then to guilty gentile people. Likewise the Bible says (if I recall correctly) that Jehovah cleanses his holy sanctuary first and then cleanses other areas.
The commentary edited by Dummelow called A Commentary on The Holy Bible (1909), on page 470 in regards to Jeremiah chapter 25 says the following. "The prophet advises submission to Babylon as God's agent, but promises its overthrow at the end of the seventy years' captivity which impends. He announces the judgement that shall descend on the nations.' However, in regards to verse 11 and the expression of "seventy years" the same commentary book says the following. "The Jewish love of round numbers would lead them to consider the number seventy used in such a connexion [sic.] as standing for any approximation to that amount. The captivity seems to have been, in fact, for somewhat less than seventy years."