Crew Transfer
For this free IVA system im proposing that you just press a "leave seat" button and then you can walk/floar around the ship. When you hover over a empty seat and press a "Enter Seat" button the Catstronaut will enter the seat.
Seated Careacters can be transferd between modules using a "Transfer Crew" button like in KSP. You select the crew menmber you want to transfer and the module you want to move him to. He will get autonatically get placen in an empty seat.
EVA using the Free IVA system.
In KSP you could just press the EVA button and have your Kerbal pop out of the door of the habitat module. This always felt strange espaclly for habitat modules like the "Hitchhiker Storage Container" as it would inply that the entire module gets depressurized.
To go on EVA you have to go to an Airlock module. The Airlock would function like in real live. It would consist of a EVA prep area were the Catstronauts suit up, It would have "seats" to allow them to be placed there using the "Transfer Crew" system. Tis is so you done always have to float from one end of the space station to the other just to get to the Airlock. When your Catstronaut is seated i the Airlock you can press a button to suit up. You then have to enter the acual Airlock portion, close the inner door, depressurize and then open the outer door. When getting in you reverse the process. For Capsules the entire Capsule acts as the Airlock.
