I know when the two parties split there was a lot of "Scott is irreplaceable" etc., but I believe this is actually true in one regard. Not because he is a dynamic frontman, there are others who command a stage. Not because he is the greatest lyricist of all time, I love him, but there are other talented songwriters for sure. The reason Scott is irreplaceable is because his voice is extremely unique.
Ask yourself this: Have you ever heard someone do a cover of a Weiland song and it not sound weird? More so than almost any other modern rock vocalist, Scott's songs sound quite strange when he doesn't sing them. Scott doesn't have the greatest voice in the world, but it is definitely uniquely him.
I think VR's comments back this up. They said they have been close to having a singer several times. They said they even wrote and rehearsed with several guys, but in the end something just didn't click. I think the problem arises when they start rehearsing the old songs, and the VR guys hear what every one of us has heard in the past when someone other than Scott sings his songs...it just doesn't sound right. Dave even alluded to this last month in his interview when he said getting rid of Scott seemed like the right move at the time. If they are going to keep the name VR, then they have to playthe old songs. More and more this looks like a lost cause.