As I know, the Osmanthus heterophyllus might be the
most cold hardy Osmanthus. On some database it is listed
as Z7, and on others it listed as Z6.

The fact is, if matured, it should be fine on Z6. So if
you carefully protect it for the first year, you can have
it.

Os can grow like a oak tree. You can manage to grow it in a proper pot which will modify their growth rate. Then you can try to espalier the plant.

Now I am very much in the mood to collect Os cultivars. I have one in my passive green house. It is starting to form a clusters of white flowers now.

The size of Os depends on the weather, in cold area
like Z6, it will not become a oak size, but will be some thing like 10' in tens of years.