bind 1 "qslot1"
bind 2 "qslot2"
bind 3 "qslot3"

alias qslot1 "slot1"
alias qslot2 "slot2"
alias qslot3 "slot3;alias qslot1 fswitch1;alias qslot2 fswitch2"
alias fswitch1 "use tf_weapon_l*;use tf_weapon_s*;use *;alias qslot1 slot1;alias qslot2 slot2"
alias fswitch2 "use *;use tf_weapon_l*;use tf_weapon_s*;alias qslot2 slot2;alias qslot1 slot1"

This can be used while also modified accordingly on demo, pyro.

https://wiki.alliedmods.net/Team_Fortress_2_Item_Definition_Indexes