Could make for a really interesting new primary weapon.
In the case of tear gas, make it a crate weapon, with the tear gas blurring enemy vision and doing low damage over time. The major drawback is that the weight of ammunition is very high, and reload is considerably slow.
In the case of smoke canisters, should be able to be found in normal loot pool (though with the frequency similar to DBS or Saw), and fire the same ammo as M79. Allowing you to quickly create a large field or line of smoke.
This would very quickly shake up some metas!