Webber has some good points and some bad points. Mainly bad points.
BAD POINTS 1. The new material. Cut it. It serves no purpose other than to beat a dead horse. Let's not belabor the points already established elsewhere in the script and score.
2. Cutting material. Come on. No-brainer here. If you cut "King of the Forest," you better give your Cowardly Lion something to compensate, if not in material then in his weekly wage packet. That's where the Lion earns his bread and his reviews. If you cut "The Jitterbug," there goes a big mood lifter at one of the darkest points of the second act, something that would be better Witch material than...
3. ...this pile of ****. Whoever decided not to tell ALW that his and Rice's style would not mesh well with Arlen/Harburg/Stothart clearly needs to be fired from RUG, as quickly as possible. In fact, the more "no" men/women that can be hired at that company, the better.
4. Okay, I get that Michael Crawford is a star, but that doesn't count for much when you gave him a glorified bit part. How about just letting him double up in several roles a la Frank Morgan in the film rather than writing new songs for him? If you need to strictly follow the RSC convention to do so, you could always make him Uncle Henry (who traditionally doubles the gatekeeper in the stage version) as well, though I don't know how good they'd be with the quick change into Marvel's outfit.
GOOD POINTS (and he really didn't have any, so I was scraping the barrel here)
1. The first act closer kinda would be more dramatic if intermission came after the "bring me the broomstick" scene. Intermission coming after "The Merry Old Land of Oz" was really rooted in other stagings of the RSC version, sending the audience out to the lobby singing along in true panto fashion. If you try to turn it into "theater" like Webber did, this is technically a good idea.
"There is no problem so big that it cannot be run away from."
~ Charles M. Schulz