Lets evaluate the SMG and see how 'classic' it really is.
>Unnecessary replacement for AR in H2.
>Irrelevant in H3.
Very classic.
Honestly 343 did a good job balancing the sandbox in H4. Considering the variety of weapons they have there are hardly any redundant ones, the SMG certainly wouldn't be needed.
The Primary weapon in ODST was the Pistol. Although I'll admit I did like the SMG in ODST it was completely different to what it has been in the main games.