Hi e - I’m sorry I’m pressed for time right now, but if I may I would like to recommend that you look at the folowing website, at two articles; the first one is a response to ch. 3 of their new book, “What Does the Bible Really Teach?”, and gives a Catholic perspective on the JW version of “Paradise”
catholic-forum.com/members/popestleo/bibleteach3.html
The second is a longer article from the same web site and is entitled “Is Your Hope Bible Based?” which examines the JW “two hope” teaching, but in the process it examines the idea of two separate destinations for redeemed mankind:
catholic-forum.com/members/popestleo/onehope.html
A specific answer to the question “Why would God change his plan?”, may not be given in the above articles, but they contain a lot of very good background information related to the subject.
Of course, the above question assumes that the orthodox Christian position is that God *did *“change his plan”; (not true). Related to this, many people don’t know that the JWs have a very different understanding of God’s foreknowledge; they believe that when He created Adam and Eve he exercised “selective foreknowledge” and
chose not to know that they would sin. Effectively, He did not know that they were going to sin, according to the JWs. This mistake colors the rest of their thinking.
I would suggest to you that at the root of the issue is the question; are there two separate, distinct, different hopes for redeemed humanity(as JWs teach), or one? The article I linked to above shows, “one”.
At that point, the question of exactly what it will be like comes into question, but John tells us that “…it does not yet appear what we shall be, but we know that when he appears we shall be like him, for we shall see him as he is.” (1 John 3:2 RSV).