I just got the catalog from outwater.com and they have just about everything. I think I saw deck railing in there too.

You've provided pictures that show a lot of traditional woodwork and built-ins (as well as a traditional style exterior), so it's kind of hard to picture it all gone except for the front door, which I'm not sure is even pictured in the photos. But if you like an eclectic look and already have sleek, modern kitchens and baths, there's nothing wrong with making your stairway match the other modern spaces. For me I think it would be too jarring to try mixing Tudor with super modern finishes (and I consider myself pretty eclectic), but I have friends who've mixed similarly disparate styles in their home and they're quite happy with the results. I agree that a designer to help with an overall plan would probably be a good investment.

It seems to me to make most sense to put one handrail near the garage.

I'd want the posts built into the framing and the tile put around.