Hi Windekind,
Thank you Meepledrone for placing this in wikicarpedia.
My pleasure... It's always great to expand the information available.

1) The question now is if you place a normal meeple on the acrobat space, can you also place a phantom on the acrobat space?
2) Or would it be rather if you put a meeple in the field, road or city, that you can then place a phantom in the acrobat space,
3) or vice versa?
My reasoning is as follows as there is no official rule for this: Normal meeples and phantoms can be placed as acrobats after placing an acrobat tile or any other tile adjacent to an acrobat tile (provided that the acrobat space has zero to two acrobats.) The main property of a phantom is that can be placed as normal meeple or as a second figure during one turn. Thus this should work as well for an acrobat space taking into consideration all the possibilities:
>> Deployment of one figure (let's say a normal meeple or a phantom for the sake of simplicity) only in the turn:
1A. Normal meeple deployed on a feature.
2A. Normal meeple deployed as an acrobat
3A. Phantom deployed on a feature (no other figure deployed)
4A. Phantom deployed as an acrobat (no other figure deployed)
>> Deployment of any figure (let's say a normal meeple for the sake of simplicity) plus a phantom:
1B. Normal meeple deployed on a feature + phantom placed on another feature.
2B. Normal meeple deployed as an acrobat + phantom placed on another feature.
3B. Normal meeple deployed on a feature + phantom placed as an acrobat.
4B. Normal meeple deployed as an acrobat + phantom placed as an acrobat.
Case 4B, for example , would allow you to deploy a normal meeple and a phantom to one or two different acrobat tiles (on the same tile and/or adjacent tiles.) Unless HiG provides a ruling limiting any of these possibilities, the interpretation of the rules would allow these cases to happen and players would not find them awkward or forced: if a player can have more than one meeple in one acrobat pyramid, should there be any limitation in placing them in the same turn? If one of them is a phantom, my answer is no.
Note: There was another thread that discussed a similar case related to The Fruit-Brearing Trees and the phantom. The conclusion was that the interpretation of the rules would allow both one meeple and the phantom to harvest from all adjacent trees in the same turn.
http://www.carcassonnecentral.com/community/index.php?topic=4179.msg62841#msg62841Hope this helps!