This is more of an enhancement rather than a real issue.
But, just like the Half-Life 2 mod, it would be nice to have a manual reload of weapons (ejecting and taking out a mag from your shoulder, loading shotgun shells from the bottom, etc.). That and maybe a two-handed mode to hold some larger weapons steadier.
Side note: The viewfinder on the shotgun is a bit confusing. Maybe it can be modified, or I might need an explanation.