I'd like to see a young companion not from earth.
...I want to see The Doctor's granddaughter Susan Fordham make a return to the show to see how she reacts to her 'grandfather' being a woman now... I know that she'd be well aware that Gallifreyans can change sexes but still... it would be fun to watch...
...another scenario is Captain Jack meeting The Doctor as a woman... imagine him trying to bed her lol!... the dynamics would be amazing between them...
...and... what if Donna Noble met Jodie's Doctor?... how many different ways could that end up playing itself out?... lol!...
...and finally... Missy better meet the new female version of The Doctor or heads will roll!... imagine the cats claws coming out of Missy more so than she's ever done before lol!... cheers.