Reply to Kovoschiz:
Again, let's take the Carto as an example of data parser understanding (not "map for renderer"). Only `aeroway=terminal` + `buidling=*` is understood correctly to be rendered as the expected deeper color (usually used for public transportation buildings) described in Wiki. This is documented usage. So before `aeroway=concourse` is discussed  (not only by two of us) and documented formally, I do not think it is proper to substitute the current practice of tagging all buildings used for checking in, boarding, or baggage stuff as `aeroway=terminal` + `buidling=*`. It will cause data misunderstanding.

To my knowledge, if we want to deal with the overlapping problem, we should use `type=site` relation instead of `type=multipolygon`. Accepting `type=multipolygon` is a compromise to the practice.

Back to the cases raised: 
1. Unnamed terminals: small airports data are highly possible to be not maintained well;
2. BRU: Structurally, the terminal consists of 4 connected buildings. It's proper to tag them separately. `aeroway=terminal` on a `building=*` describes the property that the building is used for passengers to transfer between aircraft and ground transport. the connecter building clearly takes part of the responsibility for transferring passengers from Pier A to the main building. As for the 5th one mentioned, I don't think that is a `=terminal` since it not serving passengers.
3. CDG: The liaisons are in the same situation as the BRU connector I think. The separate building of T3 follows "`aeroway=terminal` on a `building=*` describes the property that the building is used for passengers to transfer between aircraft and ground transport."
4. CTS: the connector is in the same situation as the BRU connector. The building is structurally independent.

I don't think an `aeroway=terminal` has to be the whole "terminal" in operational concept, instead, every building used for the purpose of checking in, boarding, baggage stuff or so should have the `aeroway=terminal` tag to specify that the building has such function.