Yea, i agree it pretty much HAS to do both with emphasis on combat, at least that does seem like the most sensible approach.
If there's any type of game format appropriate for that kind of diversity, it's definitely VtMB format (hub based, hand-crafted, 0 grinding, few but overarching quests, basically a finely crafted, controled environment). By now we know it didn't achieve all it set out to achieve mostly due to a very troubled development cycle.
But i wouldn't call it inefficient, it's validity has been proven, more recently through games like Fallout 3, 4 even though i wouldn't say they were the main selling point. But in a game like Deus Ex or Bloodlines? Non-combat options are kinda integral to the design. This is what people might be expecting as well, since the previous games in the franchise had them (didn't play VtM:R so might be wrong on this one).
"Inefficient" insofar as all of that lovely development would be put into options that have a great chance of being ignored or under-appreciated. But again, only if the title is marketed to a "mass audience". Instead, I'd rather focus on a title that's marketed to the niche audience that would be most likely popularize it.
Some of the games you mention like the original Deus Ex, VtM: Bloodlines, and I'll add Fallout 1 and 2, Ultima 4-7, the Gothic series, pretty much anything by Spiderweb Software -- in short, the "old school" CRPGs -- were never marketed to the "mainstream". There was no "mainstream", really, when most of these games were made. There was a budding market for games, and developers targeted a
genre. I'd argue that the Action genre is what made games "mainstream". Naturally, everyone started putting Action mechanics in everything, because they knew it would sell the most.
Nowadays, I think the entire industry has both expanded and matured enough that there are plenty of ways to be successful without worrying about "dominating the market". Like any business, all you need are the loyal patrons that keep you going. I say a title that offered such role-playing would be very successful. Just not #1.
For the new Vampire game (whatever it may be), I agree it would benefit a lot by exploring such ground, but I doubt it would be the equal of the combat systems. Obviously, anything VtM would wind up generating instant mass-appeal, and the masses would probably be in an uproar if the combat wasn't stellar.