Ambitious! Nice looking terrain and battle.
But it does look a mite open for Teutoberg Wald.
I think that the weather had an equal effect upon both sides, so any sniveling by Roman "fans" that it contributed to the Roman defeat does not hold up, imho. How many archers did the Romans have to begin with? Not a decisive number I am assuming. Probably not that many more than the Germans had all told.
"Sinew" strings. How do we know this detail? When did plant fibers become preferred as bow string material? Plant fibers do not lose their shape nearly to the degree as gut, sinew or rawhide strings. (This is just a question because I am always curious about this detail whenever anyone claims that the weather ruined the ability of bows or crossbows to operate effectively, and it's usually one side that gets screwed by the weather messing with their weapons, e.g. the Genoese at Crecy, but not the longbows of king Edward.)
If I were to play this out, I'd have the Romans trying to break out of the forest into open country as the first scenario, with their units strung out along a narrow track, flanked by hordes of German light infantry raining javelins from the trees and making rapid strikes where it seems advantageous. If the woods slightly further back are impassable to heavy infantry, then the Germans can decide where and when to engage in melee, and they get a bonus of protection from the trees from any limited return pila. The Legionaries run out of pila right away, while the Germans have a virtually endless supply of hand missiles. Allowing the Legionaries to reuse a portion of the German javelins would be reasonable. Once the legions break out into the open country, the first scenario is over, the Germans will not fight in the open, i.e. they will not leave the trees.
The second scenario is that fiasco of an artificial pass, where the Romans must move down the length of a fortified flank with hordes of Germans behind it, while the Romans are on horrible ground which forces them into loose formation, i.e. "open order" for all intents and purposes. The Roman players will have to suck it up and play a doomed battle, hoping to get off more of their troops than their historical counterparts did. There should be little if any chance of carrying the fortifications because of the protected, massed Germans vs the disordered Legionaries. Any Roman figures getting over the "wall" faces fresh enemies on both flanks as well as to the front, i.e. outnumbered two or even three to one.
But more than the terrain in either scenario, the German advantage is in overwhelming numbers. There should never be a parity or else the game isn't "Teutoberger Wald". Herman put his troops where they had numerical superiority before they attacked. This was easily done since they knew their own forests, knew how strung out the Roman legions were, and chose where to hit them hard….