I don't know if "on the way!" will work, properly, because the game trigger for knowing when you're firing is the mouse click. As soon as that happens, it will fire the round, and you'll get the gunshot sound, and it will happen the same time as 'on the way' would happen, so you wouldn't really hear all of it, and it' would end up lasting longer than the shot itself. I think the main reason why they have the "round UP!" sound isn't even for the immersion factor, which it does help with, but for a supplemental audio alert when you're reloaded, in case you're not looking right at the reticle indicator, especially when you're trying to bob and weave and stay alive in the middle of a fight.
For an immersive experience, I have found that Engine sounds, gun sounds, turret traverse sounds, and hit sounds mods really do quite a bit. Although a few times in some large brawls, the gun sounds caused some severe interruption to the game, so I uninstalled them. This is on a pretty robust computer (i7-4770k, 32GB RAM, SSD, 2GB video).