Allow use of regexps for table prefixes in settings.php

I just wondering what you guys think about allowing use of regexps for table prefixes in settings.php? I had to use it for cases where most of tables were shared except few. Specificaly I had to separate all cache_* tables. I am using Drupal 7 and achieved this by slight modifications to setPrefix() and prefixTables() to use preg_replace instead of str_replace. Just wondering if D8 might benefit from this feature as well may be?

Patch attached for D7. D8 was changed so it will not apply as is. I just providing it to better describe feature I am requesting.