This has been brought up before and it really does need improvement. Second time playing the flight and i just dont bother trying to pick a grenade i want or even look down at that corner of the screen with everything crammed down there. Even when i watch youtube videos ive never seen anyone successfully switch grenades during a gunfight, nobody does during the heat of a battle. This doesnt be a problem when fighting an enemy player though, you just throw any grenades you have and hope for the best. With Vehicles on the other hand and the anticipation of BTB this weekend, being able to switch to sticky grenades so that you can stick a vehicle or emp a vehicle shouldn’t be difficult at all and can be crucial for gameplay. The D-pad has 5 different mechanics crammed into 4 buttons, resulting that D-pad 
isnt really “to cycle through grenades” when pressed it opens up a sub menu! that brings up two buttons choices to pick which grenade… this is unnecessary and i have no idea how it made it into to this build of the game. So its difficult to see 343 NOT improving this. At the moment we have
D-pad 
helmet light/mark
D-pad 
drop weapon
D-pad 
A.I. scan
D-pad sub menu!!!
Out of all these mechanics the most obvious choice to remap is DROP WEAPON!! This should be removed from the D-pad because its terrible while being in a gunfight and you accidently drop the weapon your using. It should be a two button combination. Drop weapon should be LB + RB or to press the two thumbsticks in, somthing that is simple and that can free up another button on the D-pad.
This is already looks a lot better.
D-pad helmet light/mark
D-pad cycle grenade
D-pad A.I. scan
D-pad cycle grenade
This would be greatly optimised for gameplay for campaign and definitely for multiplayer.
I actually looked into this a fair bit since this wasn’t a issue in the first flight.
In the settings tab you have the option for grenade switching for the Campaign & it lists all of the different D Pad buttons for each grenade type. I’m assuming you can hold every type of grenade in Campaign.
However in MP you can only hold 2. 90% of the time a press on the D Pad would switch the grenades. Just like that. No sub menu.
I think this “sub menu” is actually a bug that’s cropping up from the Campaign UI & had crossed into the MP UI. I say this because it appeared very inconsistently and the settings for Campaign & MP had different settings for grenade switching. MP only having a single button to toggle between them whilst campaign had the option for a dedicated button per grenade.
Yeah it actually fixed by Sunday to just be one tap.
I’m sure this is just as Don said above, a bug from campaign. I would like the option to just cycle in campaign/custom games too with a tap of the dpad.