Everything is possible...

The API extension (Application Programming Interface) enables almost everything in TYPO3 to be specifically adapted to customer requirements, without needing to alter any TYPO3 program code. The big advantage of this approach, furthermore, is not only that new extensions can be adapted to the T3 Core, but also that other, already existing extensions can be engaged through these new extensions and thereby undergo performance improvement and optimization. The API extension offers all necessary attachment points for extending the functional range of TYPO3.

In principle, anything is possible when developing and connecting up extensions via the AP Interface!

Through the "t3lib_extmgm" class, new extensions can be easily registered and linked up to the TYPO3 core. By using any of the numerous core interfaces, a wide variety of TYPO3 properties and parameters can be influenced and adjusted to suit specific customer requirements. Developers are thus able to adapt or modify TYPO3's look, database behavior or Backend characteristics.

More information on the TYPO3 Core API can be found here...