Billy is getting massively under-rated. He was the 2nd highest tackler in all the 6N, joint with Jonny Gray and just 3 behind Robshaw. I'd bet he was one of the top carriers too. His over the ball game is getting better and better too, 3 turnovers I think it was in the AP semi-final. He's picking his moments to hit rucks far more intelligently and makes a mess of them, I remember a great one he forced against SA.
He doesn't hang back like Morgan because we don't use him that way, he stays in the line and makes an absolute ton of tackles. Same with Picamoles, Picamoles picks up a ton of big carries because he runs at centres or wingers whilst seagulling. Billy V is pretty much one of a kind, he can take that static, backfoot ball, one out from the ruck, charge into 3 forwards and still generate front foot ball. Sure we could send him against the midfield (as he was used more at Wasps) but it would mean he's no longer providing that one of a kind service so close to the breakdown. Morgan tends to go through the midfield more (or hang back in defence. I seriously rate Morgan (at least in an England shirt), but he's a different player to Billy, and I'd rather have Billy for what he offers.
What is going to be fun is if we see BV and Morgan at 6 and 8 as Lancaster has suggested, that will give us big power runners close to the breakdown and a bit further out (Ewers and Waldrom basically), one to Billy V, front foot ball quickly out two to a charging Morgan, then 3rd phase against a hopefully retreating defence. Replace Morgan with Hughes next year and that's the lineout presence too (assuming Hughes makes the step up).
Ewers is basically in the mould of Billy V for me, little use in the lineout, massive carrier even in the heaviest traffic, but until Ewers is better than Billy V, or Billy V moves to 6 (changing what we want from our 6), I don't see him getting a look in.