May I ask why, in the long term, it would be impossible for anyone to work in the library alongside the We?
In the long term, the candidates for any position in the We-run library would be between an added iteration of an effectively immortal hive-mind that knows everything about the library and can be in constant communication with every other librarian, or some guy who has none of that.
Oh cool. In canon only two Colleges have these and (iirc) the Hysh ones were actually only invented later in history by someone who within the Quest is now dead. Does that mean that there are actually many different devices akin to the Luminark (or at least 8+) and that the Luminark was mostly special due to going above and beyond in quality (compared to the previous go to Hysh battle altar)?
Canon implies that there's more Battle Altars than the two ones that models and rules were made for, probably to leave the door open to adding others if they wanted to later. By extension the general category of 'Battle Altars' would be an enchantment meant to be able to cast a Battle Magic spell several times in quick succession, and the complexity of such an enchantment results in something the size of a cart and powered by power stones or an Orb of Sorcery.
Jovi Sunscryer did not invent the Luminark, he just built one.
I don't ask you to invent it right now, but would Mathilde know the Ulgu one?
Yes.
Firstly powerstones: would it be possible to gather all the patriarchs at once when we reveal the orbs?
Probably not, since they're busy people. Alric is off searching for something impressive to do, and Paranoth is called the Wanderer for a reason.
Secondly the we: where would the we build their nest if they win? In the library itself or somewhere nearby?
Likely directly above or below it.
Would the we change to adapt to their... Job? As in would they for example, get smaller, more dexterous claws, less food intake?
Even if it is over a long timespan?
The Egglayers of the We have a fairly long life-cycle, especially now that they're on a Warpstone-free diet, so there's unlikely to be any kind of visible results of evolutionary pressures in any practical timespan.
Also how would Mathilde as head librarian integrate into the library we? Would they see her as part of it? Or as a outside influence? Would the we accept changes to initial rules of their library after some time?
It would see her the same as the current We does, because it will start off as pretty much an identical being to the current We - a particularly many-echo not-We-other-We that is part of the same Karak-We as them, who offers strange new forms of hunting and sustains the current many-food. It is very likely to become more flexible as its understanding grows.
I worry that this might functionally be "trying to have ogre + eat onion", but if Local/Orphan/We or other such group win, will we be able to get a small core of professionals to assist or at least act as trainers?
Mathilde will organize teachers if the option that wins requires them.
No one seems to be talking about this, so I'm starting to think I'm misinterpreting it. Wouldn't filtering out the Winds from a stream of Dhar(-laced) magic be a huge deal?
The stream is a core of Dhar being orbited by varying numbers of Winds. The Winds never actually touch the Dhar.