Plants I'd like to try:

Arundo donax 'Peppermint Stick'
Giant Reed (my photo from Chanticleer)
this can be grown in a big pot -- see Louis's info
found on Louis the Plant Geek

More compact than regular Knautia, 'Mars Midget' -- more uniformly colored, deep claret. A little spot of rich color in the garden. magical when backlit by sun.

Acer Palmatum 'Seiryu'
Green Dragon Japanese Maple
10 feet tall, 6 to 8 feet wide, great fall color.
Open, airy. Perfect size. Might need shade.