1) A lot of the gear quests are already listed on the forums, under custom gears. Quite a few of these have starting locations, or screenshots that show the location pretty easily.
2) Once again, a lot of these quests are mentioned on the forums under custom gears, or under ToH for Allegiance points. The resource is already there. If the player does not read it, we are not to blame.
We always stress the impotance of reading the forums, even if it is just the Announcements/Server Information and ToH parts to the player base.
If players cannot be bothered reading the forums to find these exist, I don't see them easily looking up the Wiki when they can just ask again and again on main.
3) You seem to have misunderstood what I meant. I said from a technical angle, as in, the actual scripting that goes into it, which would be what the Guide Writer read to get the quest steps, instea of doing the quest, if we gave them the script (which we won't).
Thana doesn't even require the members to be in the same party. It is all a simple area check.
There are much more technical (again, script side) custom quests out there, or coming out, than Thana.
4) It's been doable since Halloween 2008.
As for details, you'll have to find out or ask players. It starts in Yuno.