Interesting premise. But I think when you said "explore the universe" and "all sorts of interesting game play" you made game producers, artists, and a experienced programmers have a heart attack.
But then I stopped to think about it. I haven't read Journey into the West either, nor did I go read the wiki link, decided to read your game premise on it's own merits. Perhaps as episodic game play, your idea could work. Corners would still need to be cut for art production and engine design but, currently, people don't expect pure AAA quality from an episodic, DLC-style, game. So you could actually focus new and innovative game play each episode, as well as interesting plot.
Still sounds ambitious though.
Also I'd hope Tripitaka would be useful, being a repository for a large amount of Earth's futuristic knowledge, rather than a huge escort quest. I hate escort quests.