I was recently thinking about how PTA first met DDL. If I recall correctly, Day-Lewis really admired Punch-Drunk Love, passed along some glowing remarks to Anderson, and that eventually led to them collaborating on There Will Be Blood. Do I have that right?
I'm really not sure what type of movie Phantom Thread is going to be, but perhaps it's the eccentric, romantic love story that DDL wanted all along. This is not to say that he didn't gravitate toward TWBB; interviews suggest DDL had a real affinity for that material. It is interesting, though, that Anderson's most optimistic and explicitly romantic movie, which is opposed to TWBB in many ways, drew him into the collaboration in the first place.
At any rate, I'm really excited to see a strain of romanticism come to the fore in Anderson's work again. It was definitely there in The Master and Inherent Vice, but it seems like Phantom Thread's romantic aspects will be much more sustained and explicit, whereas there were a lot of other things competing for our interest in the last two films.