The Query Cache could perhaps benefit from a smarter, dynamic, query_cache_min_res_unit. In fact, it may be more useful to come up with a dynamic algorithm, per query, to determine the size of a allocation block, and enforce a "query_cache_MAX_res_unit".

SELECT COUNT(1) FROM test - Allocation block should be tiny
SELECT * FROM test - Allocation block might be "Avg_row_length" from table stats
SELECT col1, col2 FROM test - Allocation block might be "Avg_row_length" from table stats
SELECT col1 FROM test - Allocation block might be "Avg_row_length" from table stats

For more complicated queries where a reasonable estimate isn't possible, or cases where the "average_row_length" is large, use the max_res_unit.