OOC: No "edit post option", so the only option to update is to post a new reply. Think, that it is better to dispense wwith AR-70 and add a GAU-3 since the latter mentioned in Tiberium Wars (C&C3)
Again, my guess on weapons might have been used in TW. Assertions are based on contries alleigence as the onset of war as per http://vignette2.wikia.nocookie.net/cnc/images/2/2f/Stronghold-gdi.jpg/revision/latest?cb=20130331174135 and http://vignette2.wikia.nocookie.net/cnc/images/a/a1/Gdilandsinestonia.png/revision/latest?cb=20130411145007
(the following is my guess only, not EA-approved official canon)
So we get the following:
1) "Minigunner"
1a) GDI
As for start of the war they have a mixture of assault rifles, supplied by the GDI-aligned countries seconding their troops to GDI command service. 5,56x45mm ammo set as standard for assault rifle ammo. These may include Colt M4A1, Enfield L85A2, H&K G-36, Steyr AGU and Kalashnikov AK-101/AK-102.
As GDI is turned into a more unified force with it's own supply chains, under GDI's Council decree the H&K XM-8 variand is adopted as GAU-3 "Eliminator" assault rifle to become GDI's standard service rifle. Rifle is again chambered in 5,56x45mm
These are supplemented with FN Mk.48 Mod.1 LMG (chambered in 7.62x51mm) as squad-level support weapon and H&K USP 9mm pistol as backup sidearm.
Note of interest: The ultimate irony with GAU-3 "Eliminator" was that GDI have stockpiled lots of GAU-3 rifles until it was phased out of service in favor of M-16 Mk.2 pulse rifle shortly before the Second Tiberium War. The rifles were stored in military depots, that were abandoned and put in conservation as part of GDI Council's defense budget cuts after Second Tiberium Wars. After GDI Military left, the depots were captured by Nod, and GAU-3 rifles stored within were used to arm some of the Nod's own volunteer militants forces, so the rifle seen action as late as Third Tiberium War.
1b) Nod
Considerable part of the armouries consist of requisited (from Nod-aligned countries armouries) Warsaw Pact (and their immediate successors) armaments, consisting of 7,62x39mm Kalashnikov AKM/AKMS (and their close clones), however, these "stop-gap" weapons are gradually replaced with Norinco CQ (an M-16 close clone), chambered in 5,56x45mm, as a Brotherhood armies' standard service rifle. Captured arms are also used willingly.
These are supplemented with Zastava M84 and Vector SS-77 7,62mm machineguns as SAWs and Beretta M92FS handguns as backup sidearms.
2) "Grenadiers"
These guys probably get an Armscore MGL-6 grenade launcher and a H&K USP 9mm sidearm for self-defense.
3) "Engineers"
These are specialists, generally not meant for direct frontline combat. As such they are equipped with a sidearm (USP for GDI and Beretta-92 for Nod), but may be equipped with assault rifles if need arise.
4) "Flamethrowerers"
Typically armed with an LPO-50 flamethrower and Beretta M92FS pistol as backup firearm.
5) "Commando"
5a) GDI
Outfit is mission-specific, but may include Accuracy International AWM .338 cal sniper rifles for long-range engagement, H&K MP7 PDW for close-range and as back-up firearms, and C4 timed/radio-controlled explosive charges.
5b) Nod
Outfit is mission-specific, but may include Izhmash SV-98 .338 cal sniper rifles for long-range engagement, B&T MP9 SMG for close-range and as back-up firearms, and C4 timed/radio-controlled explosive charges.
6) "Rocket soldier"
Armament most likely considered of a 9mm pistol (H&K USP for GDI and Beretta 92FS for Nod) for self-defense and a Rafael Mini-Spike shoulder-mounted missile launcher, capable of shooting both anti-tank HEAT rockets and short-range surface-to-air heat-seeking missiles.
7) "Chem warrior"
Some sort of tiberium-based chem sprayer, shooting tiberium-based toxin via compressed air.
NB: During the First Tiberium War existence of chem warriors was officially denied by Nod Brotherhood's Inner Circle (becouse of toxin usage violation the UN's chemical weapons prohibition convention) and in case of capture Nod's Public Relation division was quick to disown such soldiers, denying any connection with the Brotherhood.