Any Need?
In a combat rifle - maybe.
Civilian rifle - Most cases no.
The dust cover is not necessary unless you plan on dragging your rifle through mud.
The forward assist is for a combat situation where your rifle fails to go bang. If a round fails to chamber properly the FA can force it in battery and potentially cause catastrophic failure. If your rifle fails to fire during a day at the range it is time to stop and investigate why.
In combat its another story. In the U.S. Army we called it SPORTS:
Slap the bottom of the magazine.
Pull the charging handle.
Observe the open chamber area.
Release the charging handle.
Tap the forward assist. Shoot.
There are some hunting situations where the FA can be useful to chamber a round quietly by slowly releasing the charging handle and the using the FA to make sure it is in battery.
Just my opinion. Getting a new upper just to get a FA and DC is an unnecessary expense.
Plus if you do get another upper, it won't be long before it gets lonely and you get another lower for it.
