GERMANIC ALTERATIONS
Having gone over various sources these are my rough ideas as how to bring the Germans more into historical lines.

Generally Germans of this period should be pretty poor off when it comes to arms and armour. Gauls have been directly trading with Rome, Carthage, and Greeks for sometime and all the Germans get is what they can trade off the Gauls. However what the Germans lack in arms they make up for in ferocity. So across the board German Units could use a general drop in armour values and an increase in the affects of the War-cry bonus

Infantry
Ok this needs a rework, the Phalanx of Spearmen is of hotly contested historical accuracy, Axemen and Berserkers feel akward additions which try to tie in with later Nordic types.

First Tier Unit
Germanic Warband
Germans fought with Spear yes but not in a ranked formation. More suitable Germans should throw spears before hand to hand much like Romans.

Second Tier Units
Germanic Veteran or Hardened or some sort of elite sounding name Warband
The more seasoned warriors, have better armour and either purchased or stolen swords or other sorts of hand weapons.

German Raiders
Raiding and Slave trading seem quite common among German tribes however losing the current uber status Night Raiders have would pull them more into historical lines. Still fast, still armed well, but just not as good as the current ones.

Third Tier
Chieftians Warband
These are the veteran retainers and elite warriors of oe of the many petty Germanic leaders. They can actually afford mail or have fought long enough to have acquired some.

Religious Unit
Fanatic Warriors or a Berserkers could be fine here.

Missile Units
Not so bad mainly some name changes.

First Tier
Barbarian Skirmishers renamed Germanic Youths

Second Tier
Get rid of the armour and the chosen bit on these archers, archery was not common with the Early germans so what few they would field would be quite poor.

Cavalry
Gothic Cav is very out of period and should be dropped, but the German use of light cav has been ignored

First Tier
Germanic Raider Cavalry
These would actually have been more along the lines of the swifter horsemen picking up a Youths and moving as mounted infantry running them as regular cav is really the only option available with RTW. So Javein armed skirmish cavalry for these fellows

Germanic Cav
Current Barbarian Cavalry

Second Tier
Germanic Noble Cavalry
Same as the current Barbarian Noble Cavalry

End Notes
Still lacking on the diversity front, but with further additions of tribe specific units perhaps some sort of Mountain Tribesmen from the Alps the list could be fleashed out and still remain quite accurate.