I think a competitor could do more with vevo than the commoditising approach of youtube.
Imagine if vevo were incorporated into facebook for example. It would be a larger audience with highly targeted ad & opportunity to sell network.
VEVO's hold is tenuous - they are no stronger than Freddie Wong/Corridor Digital/Smosh - they all rely on YouTube more than YouTube relies on them for traffic flow (nowadays anyway) - there's always someone there ready to fill audience needs if they went off YouTube.
The music video clips in question are exclusive to the studio for the contracted period, and it's this which vevo are willing to shop around. It's an exclusive product without substitution. I'm yet to find a convincing argument that a consumer will be satisfied with a home remixed version with custom graphics when they're looking for the original clip. (Or rather that they'd choose such a clip when the original is available elsewhere for free.)
As for unlicensed copies, youtube's own system is very good at taking down illegitimate versions. Additionally the studios are lighting fast with DMCA take down notices (within hours) for clips that sneak past one way or another. The system is geared heavily to copyright holders, automatically denying clips that would normally construe as 'fair use' in the USA.
I won't comment on traffic flow, since that's not publicly revealed, however it is reported to be youtube's most watched "channel", that on its own indicates that the traffic result is not due to a unique "youtube experience", but rather the result of being the only place online where the videos can be viewed for free.
This is something Vevo can shop around, I suppose what I'm conveying here is that ultimately they don't need youtube. Youtube to vevo is a commodity video service, it's network was once unique, but now other sites could handle the level of traffic that the catalogue would generate. In another thread I've listed simple examples where it could be better leveraged, possibly producing a better outcome for the studio than what youtube provides.