I not think you updated skype in a while or just not used it mate.
1. Fully separate groups on skype.
2. You for a long time now (years) can be offline but online with skype.
3. Contact history is fine and can go back 6 months. Works well, been the case for a long time.
4. Separate windows for conversations is supported in Skype. Double click the name rather then single click to get a new chat window for that person.
I think you need to check your version mate and just use it. Has all the features you think it does not have.
I use Skype every day, I even had a work account setup with credit.
1. That's not what I was getting at really, besides which they serve no purpose when you bear in mind the other points.
2. Switching offline for everyone as it is in Skype and appearing offline for certain contacts are two entirely different things.
3. Doesn't seem to work well at all for me even though I've got it set to 'Keep forever'. It's also garbage that it tries to load the history in the window instead of a nice searchable seperate message history panel going back until the dawn of time. Messenger did this much better.
4. I'm on the latest version and that doesn't seem to work at all, either in the Contacts pane or the Recent conversations pane. --- Ahh it seems you have to be in the hidden out of plain sight 'Compact Mode' for this to work...
That's much more MSN like, cheers Liam.