I would be inclined to agree that site-local programs and standardized
ports should be in separate places; it's easier to work with, and it makes
it easy to leave the "standard" port around for testing.  I normally
have my bin, local bin, and plain bin in my path in that order...  When
I have buggy behavior, all I generally have to do is reverse that order,
and then I can tell which program was acting up.

There's a fair amount of prior art for a /usr/contrib/bin, or something
equivalent.  It's a basically sound idea.

-s