That old Wiseman telling you he'll stop a rampaging Id from getting to you, even getting called out on it by Id... totally unbelievable, right? Till you consider that he is Grahf and thus the same person with exact same powers.
Realizing that the entire human race in Xenogears is was artificially created by Deus may lead to questions or Acceptable Breaks from Reality regarding how a completely isolated culture retains the same language as the humans who were onboard the Eldridgenote Evidenced not only by the in-game text and opening move but also in reading the Eldridge's data and such. Then it comes to mind that Abel was the ship's only survivor, and could have spread these cultural aspects to the Xenogears planet.
On the other hand, Deus may have made humans speak in the language it was programmed in.
The odd part is that Solarians speak their own language, and if anything you'd expect Cain and the Gazel Ministry to be the ones that would use the language Deus was programmed in.
Why does the super-gear Achtzehn have trouble fighting Chu-Chu, of all things? Because its main weapons are designed to jam gears' controls. Even when she grows to gear size, Chu-Chu is still an animal. She has no controls to disrupt.
While I admit that the final boss Urobolus feels pretty damn good seeing as you know it's really Miang. But why was she so dang easy? Was it because of the whole Disk 2 fiasco, or was it plot-related?
It was probably one of those final bosses that opted for more of a storyline-take on it like many other games of the time period, such as the strikingly-similar Wild AR Ms 2. Also, consider the fact that some players defeated a marathon of five bosses beforehand, so making Urobolus tough would have been a little overkill.
Also, Miang is part of Deus, and Deus just got a butt-kicking from Fei & company about a cutscene or two ago. She may have had barely enough power to hold herself together, much less put up another fight.