While I've already discussed this at great length on the Single Kerbal Mode issue on KMP, I did want to mention it here as well:

It should be possible to have specific Kerbal(s) bound to an account. This would mean that only account(s) defined as an owner of a given Kerbal should be able to EVA or control them.

Here is some examples of functionality that I would like to see, ordered in terms of expected difficulty/when they might be possible:

• The server stores Kerbal names and user ownership
• The server admin can rename a kerbal via the database, which is reflected on clients after resync.
• The Client allows the owner of a Kerbal to change their name. Initially this could be done with a simple /rename command while on EVA for example. Much later this could be integrated in some sort of Mission/Inspector UI.
• If a vessel's current pilot does not have ownership of a given Kerbal, that kerbal can not be EVA'd. Same for Kerbals in Pods/Lab/etc.

I think this could lead to a very intuitive permissions system, where a kerbal is assigned to another player, which would allow them to take over the controls of the vessel. similarly a player that is EVA'd and enters a vessel would also be able to request command of said vessel. If a player has none of their kerbals on a vessel, they can't take control of it, simple as that. For an even more hardcore mode, you can only spectate a ship if one of your kerbals is on board.

I like this a lot,
one more thing, If permissions are moved from Vessel to Kerbal, what about Probes ? Permissions would be applied to the probe core ?