I'm glad you like the crank and big ring
You should have no problem with the front mech if you decide to use a 50t ring, but the easiest way to tell would be to fit the crank with the 53t to your bike, fit the front mech in the correct position, and then see how far down in the slot it will go.
The difference in radius between a 53t and 50t ring is about 6mm (107.5mm vs 101.5mm approx), but bear in mind that the front mech outer plate should be between 1 and 3mm vertically from the tips of the large chainring when the chain is in the small ring, so this might give you some extra adjustment room.
Depending how much material there is around the slot in the hanger, and how good/orignal/special the frame is, you could file the slot a bit longer to fit the mech lower.
If all else fails, I do remember seeing some adaptors that fit between the hanger and mech to fit it lower down (can't remember where I've seen them though).
hope this helps!