1. The agile version of RUP is published before as dX methodology, which is so poor in comparison with other proposed agile methodologies (since the goal of an Integrated methodology like RUP is so different with agiles, therefore this mixture can not work properly;) )
2. Most important concepts proposed by agilists are their proposed practices (12 important principles), which are proposed before too, but are gathered by first proposed agile methodologies (like XP). First agile methodologies do not include precise process, but gradually they ll include processes too. They do not include extensive modeling during development, and are mostly suitable for small size projects  and small teams. Their proposed processes are different from Integrated methodologies, like RUP. This topic can be discussed deeply later:)
3. As you found out, there are reasons which makes agile methodologies unsuitable for large  scale projects, including those you mentioned. That is, the risk of using agile methodologies in such projects is high.