It's completly retarded NOT to have it.
The FAMAS F1 fires in both Automatic and 3 round Burst Fire mode, for example.
Not having this severely nerfs all weapons.
And I still love seeing guys using the Barret M107 as a standart sniper rifle when it weighs a lot and has a stupidly high recoil.
And I don't even wanna imagine how it is gonna be with the AS50, wich is basicly the most 'overpowered' of all the Acurracy International long-range rifles, making the AWSM look like a water gun.
CoD doesnt need it different firing modes.
If you want a burst weapon, pick a burst weapon.
If you want a full automatic weapon, pick a full automatic weapon.
If you want a semi-automatic weapon, pick a semi-automatic weapon.
(Almost) every gun has its own charm, and thats a strenght of this game.
Its a arcade game where the maps are small and the action is fast.
Switching firing modes would just cut into that and I think thats why they removed it from the original game.