Well depending on how street level we go maybe a phantom of the opera style love interest touchstone may be fun.
Making a touchstone would be an incredibly interesting twist. Because as a vampire you don't want your milestones to change. Ever. They ought to be cities in a bottle, eternal exemplars of whatever idea you see in them. So a love interest touchstone progressing to a relationship with you (or someone else!) is actually a fail condition. It's all sorts of ****ed up!