Automatically add Property to Object on Creation

Metadata Card Configuration should work for you. It responds immediately. I often use it in situations where if the users selects this in one property then some other property is required/not required, or additional/hidden.

Auto Calculated properties only gets updated on check-in.

However, if you want those properties to always be available on a number of classes you should really take the time to add them to each class. I know it is a boring task, but it will make things much simpler for you and the users in the long run. So grab some coffee and get on with it ;-)

Have to check, why Metadata Card Configuration doesn't react immediatly in my case.. For adding the properties to many class, could we achieve it via power shell script?

Don't know about that. For me it would take longer time to create the script then to edit the classes manually. It might be more fun to do the scripting but unless you can use the same script for multiple tasks I wouldn't bother. You can edit really many classes (hundreds) in a couple of hours if you can keep up the concentration.

However, it would be great if Admin were improved to allow simultaneous editing of multiple classes.

A simple but effective improvement would be to allow selecting multiple properties for copying and pasting..

Just tried a little around but I cannot get a property added via Metadata Card Configuration when the Object is not yet created (when filling out the metadata the first time)..