I find the weapon switching with the mouse wheel or numbers (Above WASD) a little clumsy. I followed the guide below and it really improved my switching speed for med kits, rockets, engi tool, revives…
A lot of people don’t revive in BF4 just because it’s such a bitch to get to the right kit. The fix below solves that.
You can change the key bindings for gadget 1 in Battlefield 4, you just have to do a little trick. You must bind the same key to all three of these:
Select Gadget 1
Toggle Underslung Weapon
Toggle Gadget 1
Then it will work. The bind I use is scroll down and I use the middle mouse button for defibs. Enjoy!