Secondly, no. No one wants to be punched in the gut when they get shot in a video game, nor do they want to smell the gore-streaked trenches of WW1 or taste the air in the sewer level.
... not no one. There's
already some (crude) feedback systems around for some games, iirc, and there's
definitely a non-negligible minority that would be into something like that, just like there's people that like slamming into each other on a ball field. Some people just really like full contact. Plus there's a lot of tactile feedback beyond pain that would be
hella' impressive. Wind, physical textures, touch puzzles, etc., so forth, so on. And that's without getting into any salacious uses thereof (they're already working on that!).
As for the smell... yeah, there's going to be folks that want that, too. Probably even moreso than pain/etc. feedback. It would be an
incredible increase in immersion -- humans are seriously tied into scent when it comes to some things -- and there's definitely people that would be into it, even the nastier stuff.