I think it would mean a lot to Kate Stewart to meet the Doctor who ultimately started her father's UNIT journey. Because of Timey Wimey stuff she can't tell him who she is of course, but she can still show some thanks.
Bonus:
I like to imagine since Donna works for UNIT now, she likes to ask Kate along for lunch occasionally. And I also think 14 wouldn't hear the END of it once she finds out about Jamie.