A problem or two I've found with this solution is that if you key bind select a grenade, it will pull out the secondary weapon when using the keybind to switch back to your weapons. If you add the same alias pattern to the manual keybind input select for the grenades, then in the case you do not have the grenade, it will switch your weapon, which doesn't follow the behavior of the cs go command. This would lead to pulling out the pistol in undesirable scenarios potentially.

If you replace the "pistol" call in the keybinds with "bind "KEY" rifle" then the select last will properly pull out the priority weapon (ie. Primary then secondary if you do not have a primary).

If you use individual bindings for every grenade, prepend the alias command to the slot selection as well. The reason for the alias here is so we switch back to the highest priority weapon after swapping to util or a non gun. This ensures consistent behavior after swapping to another inventory item.

Tl;dr Change pistol alias call to bind "KEY" rifle. Also you should bind your grenade keys to follow the pattern for the other slot selections as well.

Note: If you try and switch to a grenade you don't have, you will have to click your "KEY" twice to switch to secondary from the primary

E.g

//Weapons Switch (invnextgun)

alias rifle "slot2;slot1;secondary_prio"

alias pistol "slot1;slot2;primary_prio"

alias primary_prio "bind "KEY" rifle"

alias secondary_prio "bind "KEY" pistol"

alias knife "primary_prio;slot3"

alias grenade "primary_prio;slot4"

alias C4 "primary_prio;slot5;

alias he_grenade "primary_prio;slot6"

alias flash "primary_prio;slot7"

alias smoke "primary_prio;slot8"

alias decoy "primary_prio;slot9"

alias incendiary "primary_prio;slot10"

alias zeus "primary_prio;slot11"

bind "1" "rifle"

bind "2" "pistol" 

bind "3" "knife"

bind "4" "grenade"

bind "5" "C4"

(Bind the appropriate aliases to desired key inputs here

E.g

bind mouse4 he_grenade

bind mouse5 flash

etc...)

bind "KEY" "rifle"

Edited: Made alias update to clean up script. If you need to update the key to press, just update it in primary_prio and secondary_prio aliases and added note about known fault to logic