I am piecing together an M16A4 clone, and have a quick question for those who have may have carried/been around A4's in the military, ideally around the 2003-2005 time period. What aftermarket accessories were available or were allowed to use early in OIF/OEF? I know VFG's, lights, buttstock mag pouches, etc. were issued and used, but were you allowed to put aftermarket pistol grips, ambi safeties, etc out of what relatively little was available at that time? I'd like this to be as authentic as possible, but be something outside the run-of-the-mill A4 build.

If you can't find the info here, you won't anywhere else.

From what I've seen, most of them were kept stock and had added things like butt stock pouches and vertical grips.

Marine Corps...4 deployments across '03-07, only on very rare occasions did I ever see anything other than standard issue on an A4 or M4.  During that time period I never saw an A4 with a nonstandard grip or other safety.

For the A4:
KAC rail with or without panels
KAC VFG, or later the Grip pod was almost universal (not certain I ever saw a grip pod prior to '06)
ACOG (usually seems armory dependent as whether it was issued killflash or not...pretty much everyone or no one has it within a unit)
PEQ...sometimes with remote switch
Various Surefires...usually with IR filter
Wild variety of slings, these were often procured outside the supply system
Sometimes a carrying handle stuck somewhere on the rail as a backup or to prevent loss.
Sometimes a PVS-14 mount

Some armories would install a badger latch on all rifles
There were a few Harris bipods floating around.
Big zip ties securing the ACOG and PEQ were required in some units.

Ther earlier you go, the simpler the kit was likely to be.   Also keep in mind, there were many units carrying A2s in 2003.

That's about all I can remember.

Ohh...yes, the buttstock mag pouch mentioned in the OP.  I always hated both the grip pod and the buttstock pouch.  The pouch was popular so rifle could be carried in rear areas, in condition 4, with the minimum 30 rounds.  The grip pods were known as "chow hall kickstands" among my friends.  Of course, these things were both everywhere by '06.

Perfect! Thanks for the info.