An (unauthorised) finished version of Alph Art has him meet a possible girlfriend. I personally see Tintin as someone who doesn't need to find a lover though. Lets face it its not like he hasn't had a fulfilling life.
I'd like to see a Tintin story involving the murky politics of the 70s and 80s. Maybe some kind of Watergate analogue.
Tintin the Spy. A take on the James Bond Craze of the 60's.
Tintin the Detective. The Thompson Twins end up framed in Jail. Tintin has to investigate the crime to free them .