Here is what I came up with:

SELECT ISNULL(ac.code, b1.code) AS code, a2.aname, b1.bname, ac.cname

FROM (SELECT a.code, a.aname, c.cname, ROW_NUMBER() OVER (Partition BY a.aname ORDER BY a.code, a.aname) AS RNO

FROM @a AS a

LEFT JOIN @C AS c

ON a.code = c.code) AS ac

FULL JOIN (SELECT b.code, b.bname, ROW_NUMBER() OVER (Partition BY b.code ORDER BY b.code, b.bname) AS RNO

FROM @b-2 b) AS b1

ON ac.code = b1.code

AND ac.RNO = b1.RNO

LEFT JOIN @a AS a2

ON ISNULL(ac.code, b1.code) = a2.code

ORDER BY ISNULL(ac.code, b1.code), a2.aname, b1.bname, ac.cname