1st - Being able to buy stores and houses / setting sale prices and rent
2nd - tattoo's!!!!! and die's to color your clothing and armor
3rd - Having a family
4th - THE SWINGER achievement / trophy!!!
5th - starting out in the game as a child building the character up certain point then time jumps to present day...in prison like usual...
changing the subject here real quick what would be kind of cool and funny at the same time would be like what they did in fallout 3...the part where you went into Hubris comic book building and you were able to play Grognak on the computer...well how about sometime in the game a Mage puts a spell on you or something and you go back and play one of the past TES games the older the better!
Any other ideas from other RPG's you'd like to see in Skyrim?