Currently dual wield only works for all pistols and PDW ,when dual-wielding other weapons,they become invisible on the left hand.
Some weapons may rely on right-click for aiming(like the bolt-action rifle),but other than those scoped weapons,others should be dual-wield-able.

No they should not. They are two-handed weapons and you can't dual wield them. Two handed weapons can only be used in the main hand.

Thanks for replying to my idea,and sorry for coming up with some weird ideas sometimes.I thought that dual-wield AK would be cool and tried posting here,but maybe it is just something not practical...