[Lava]

Now I know for tree. I also now found it in walkrhrough. Although I will test it, to see what I lose and what I gain. It said that it marks quest as completed, but there is no any quest opened about it at moment.

It's because the price may be unacceptable to some, and I wouldn't want the quest to remain unfinished for those players.

I completed a lot quest from your mod, at least for BG1. (not sure does it also bring stuff into SoD or SoA). Maybe even all, I need to check walkthrough. If any is possible only in BG City, than I did not completed it as I'm now in Chapter3, preparing to attack bandit camp and soon to be in Chapter4, as seems there is about nothing to be done (not talking only on your mod quest, but on all my install and quests). I have lot of mods so it took days to complete all I could what is possible or limited to Chapter3.

There are some quests later on -- including one of my favorite ones, which allows you to face the

Cult of the Dragon.

No, dont delete it, it is really nice work.

I'm not planning to, it was just a note on why it may stay imperfect and this one will only work fine if players do not abuse it 

I don't understand what you mean by abuse Hideout ? If you left NPCs there, I guess they would be removed once you move to SoD (after Korlazs tomb) just as it would happen if you leave them in any other place.
If you mean abuse by leaving items for purpose to not lose items as you progress to another parts of game, than indeed it would be exactly what I would do (unless you scripted it so containers get cleared upon progressing to next stage of game), as I was abusing it anyway, like I said, in Durlags Tower always before. Making it not possible would not do lot. Because players in the end will find way to do what they desire one way or another. Even if somehow all game get patched to prevent keeping items for next stage of game, I would than tweak certain things in NI locally for my play and make it possible null

But I still don't understand what did you mean by "abuse" of place, as NPCs would get deleted anyway

I'm not sure those NPCs would disappear. When you move to SoD, most NPCs are "destroyed" as you progress, but those NPCs are with you. There are plenty of instances when companions are handled by area / cut scene scripts in SoD, and if they are "hidden" from them, on that area, stored since the OC, it can get messy. As for items: nah, I wouldn't worry much about it. Technically, that area can help you store items between SoD and BG2EE on EET, I think, but then again, I leave that to the player. If someone truly wants to keep those items with the help of that area, then--it's all up to them