There will be protection for this so you cant abuse keys/maps to kill low levels.
The TL;DR of how it works is, you can only spawn the tier of boss in relevance to the area they are looted. For example, you can only Spawn T1 (Hate, Evil, Sin) in Edrona, Titanium Golems in 500+ Areas, Frost / Glacial Golems in 2k+ areas, etc.
t3 rebirth bosses in midguard+?
also now that im home i can clarify some of my opinions better
fiscos ice is currently gotten from killing fisco a second time after you already killed him to rebirth, but it was added quite a while after people were actually selling runs for fisco, and i think that the element with fisco where you either had to assemble a team, or pay some high lvl for a boost through it was good for the market, instead of just buying an item for reward tokens and insta-rebirthing (i will however say it was a nice addition after a while because people wanted more and more alts to try out and stuff, but adding it the second someone actually loots it would just feel bad tbh, it would give ppl who can pay a free rebirth and those who cant a shitty time because people dont want to carry 1 person because of the time it takes etc...)
gilded set is another thing that was added a while into the server (at a point where it was worse than most peoples set on mains of those that where decent levels) and adding it now the second boss gets spawned (not too long after someone gets 7k) would mean again, that those who can pay for an entire gilded set will have full t7 by 6k? (cant remember exactly) and t8 by rebirth (which pretty much NOONE had at the start of the server), admittedly, people will have better gear now cause of ubers and chests yes, but full t8 after rebirth is more than enough to steamroll pretty much every single rift (meaning people who collected gear before it to have good gear wont really have much of an advantage, full t8 will just be gems which xagul said will be more scarce, or t9 maybe but i highly doubt it, again, i think it should also be delayed a bit further to encourage people actually trying to get gear BEFORE rebirth instead of just buying gilded set then grabbing gear when they hit t3 bosses + ubers....
key changes are something that has to happen, and having them only spawnable on you outsize pz in the area relevant to them is a very good idea (although it doesnt stop an alt from hiding in a place where noone really goes and most ppl dont know exists and just afk botting keys, and finding out an alt of someone who is keybotting is kind of impossible unless they slip up and show it giving gear to it or such...
maps should definitely stay the way they are imo, theres no point restricting them to outside pz and relevant area and removing the rooms, you still have to actually be outside and hunt to get them, and if you want to stop someone from hunting then just afking maps on an alt (Which they hunted to earn) just restrict them to be usable by person who looted them (at t3 and above if u do that imo, since lower tier of maps some ppl tend to give away to new ppl for starting gear and such)