Hello.
About №3.
Other issue that we have with that is people trying to sell faster and dropping price low. When there is a lot of same items, people logic will be to drop price in order to sell it faster. At some point you will have an issue, that it will cost less, then it should. At this point, if you still can't sell the item, but you really want to, you will continue dropping the price. Other people won't put their items at all, because they will see a price on item that is too low for them to even get any profit from it. Same logic is behind Oil pricing. Companies making conferences where they decide minimum Oil price. They can sell it cheaper, but it will heart whole economy. Players who are selling items on auction will start earning less money from it or won't have any profit at all which will scare them from the auction.
About №4. We can't bind auction item price to CoL price because of:
CoL price is not constant. It can be up to 500k per CoL and few weeks later drop to 250k per CoL, based on CoL amount in game.
Control CoL price each time before approving item on the auction is bad. 1 day we won't be able to approve 60 euro for your Staff, because CoL price is low and next day, when price will increase - we will have to approve even 50 euro for your Staff.
Because you won't be able to change price on a go, you can't compete with items that were approve when CoL had high price. And difference can be insane. Based on your staff example it can be from 40 euro ( when CoL price is 500k ), to 80 euro ( when CoL price is 250k ).