I think that would be good for us, but probably risky for business.
A quick look at recent MMO history says the exact opposite. If you can describe your game as "like WoW, but," then you are very likely not going to succeed in any way that justifies the initial investment. The problem is that by-the-numbers design works pretty well in just about every category of entertainment available. Music, movies, and even video games most often turn a profit when it follows proven formulae, especially if it also ties into a popular IP. The difference, however, is that all of those are
consumable. You watch a movie, and then you want to watch a different one. You listen to an album for a while, but you eventually want a new album. Same thing with games...
except for MMOs.
The entire point of MMO design(one I don't necessarily agree with) is to keep you playing, and therefore
subscribing for as long as possible. This is true even of free-to-play MMOs since people who don't play your game won't spend money on microtransactions. That being the case, any new MMO has to overcome the hold an existing one has over its playerbase in order to succeed, so the copycat mentality actually works against MMO development, as just about every game that's tried to take on WoW has proven.
Once again... in MMOs, safe = failure.