These need to be change to make switching between them more intuitive especial mid battle.
In stead of having a swap menu pop up lets do this:
Grenades:
Switch to tapping 
to cycle through the grenades
Equipment:
Switch to tapping 
to cycle through the equipment.
I disagree on the cycling. I agree the switcher is not ideal but would have died many many times by attempting to activate the wrong equipment by cycling through missing the one I wanted and having to go back through the list again.
Unfortunately only so many buttons on an Xbox controller to work with.
THIS. Toggle with a distinctive sound and you have good design. Or you do it like 343 where you either have to learn button combos or look on the tiny fcked up UI… which scks as well
They could always just copy the weapon wheel/ radio station wheel concept Rockstar uses in GTA; holding the d-pad direction could just pull up a switcher that slows down time, and allows us to pick our equipment/ grenades in tight situations.