Adding and inviting friends offline (cross-server friends)

I'm unsure if this has been suggested before, if it has then sorry.

Recently I have been to gamescom and had a blast, I even met a few people from my own server.
The thing is that we can only invite each other when we are both online,
why can we not just send a friend request when they are offline so they can accept when they come online?
This makes it more easy to connect with people.
Another is to connect with friends cross-server (on the same data centre) so you can interact in-game even though you don't play on the same server.
I hope you like my idea and let me know what you think of it.

Kuro Kenshi

This suggestion is even more relevant now that we have the Contact List and cross server party finder. =)

This would only be good if we could actually have MORE than 200 people on the friend's list/blacklist.

We're able to party up with other servers, yet they did nothing about that, why?