A word latter + anagram mashup? Love it! I knew what
1A1AThis is your chance! You get to travel from ___ to 40A, without having to become a billionaire first. To make the trip, stop at 15A and 29A first. For each entry, change one letter and anagram the word to find another common word. Have fun!
[-----] had to be right off the bat, and I suspected where we'd end up at
40A, but wasn't quite confident enough to plunk it in there from the get-go. You hit on a really well-balanced difficulty level, since the anagramming meant I couldn't just guess my way down the ladder without some crossers first, but those crossers in turn came just easily enough after one or two of their own crossers. And I agree that reworking your grid to include
30A30AAbout the most massively useful thing a person can have for a trip in 40A
[-----] was absolutely worth it!