In my honest opinion, Oblivion needs a retheme. It doesn't need changing physically. Smiler has a theme with uniforms, Oblivion needs that too. It may be old but I see so many people and kids going on for the first time and in my view it is not 'old.' Just outdated and need a retheme. Nemesis is old too and I still love it having first rode it way back when it first opened and I'm never tired of it.
It's not meant to look 'new', it's supposed to be retro. Even in the 90's it was supposed to look retro.
If you want a modern take on Oblivion I suggest you visit Gardaland, They have reimagined version of Oblivion.