How it will be if we can use PDO with CodeIgniter?

Question

PDO for SQLite3 is done already. Have you got any way to use PDO with CodeIgniter for other Databases? How did Codeigniter skip PDO for other databese-servers, I dont get it. Expect you may know better and can pick us up.

EDITED: Any tricks/way to build our own PDO class is highly appreciable.