Due to game mechanics, in 0.0 only sov holders are able to place command centers on planets.
Once a command center is placed, a pilot can use PI on that planet as normal, wether they are part of the sov holding alliance or not.
Because of this, 4TH are happy to let either entire corporations or single pilots join 4TH for a very brief period in order to place down command centers on the planets they wish.
There is no cost for doing this, only the taxes applicable for use of the customs offices when importing and exporting goods.
If you are a pilot looking to do PI in 4TH then you can contact either myself or Dex Nederland about temporarily joining a corporation.
If you are the CEO of a corporation wishing to bring your corp into 4TH for a day then please speak to myself to make the arrangements.