Scripts called through eID have always been limited in terms of functionality, however new features give more options:
tslib_eidtools::initLanguage() initializes the language, making localization features easily accessible
tslib_eidtools::initTCA() loads TCA
tslib_eidtools::getTSFE() initializes the main frontend class TSFE
More info:
RFC: #9318: Enhance and fix tslib_eidtools
http://bugs.typo3.org/view.php?id=9318