I bet your car has the air suspension, right?

As far as I know, the retrofit of the Comfort Package items should be (theoretically) possible. But because there is no retrofit kit, you should expect to pay a lot of money for a retrofit. Not sure if it is worth it.

BTW: I didn't order the comfort package on my upcoming Cayenne Turbo. Why? The self dimming mirrors always annoyed me in most cars because sometimes I want to see what is going on behind me and with a dimmed mirror, you don't see much. The hatch motor is nice but do you really need it? Even my wife didn't want it.
The garage opener doesn't work with my (old) garage door opener system and the "homecoming" light is nice but not really necessary.
That said, I don't think a retrofit is really worth paying at least double (or even more) the price of what the comfort package costs out of the factory.

Don't worry, be happy.