Book involving clones, "The System", “Mama Mercury “, and an abandoned monastery on the Moon?

I’ve been searching for this book for a while, to no avail. I read it as a teen somewhere between 2005 and 2013, in the UK. From what I can remember, it was a Star Wars style “ragtag gang of rogues/rebels fighting the imperial system”. I seem to remember there was a focus on the use of clones as well. Some other details:

• Most planets in the solar system were colonised
• There was an abandoned monastery on the Moon
• The imperial government was called something like “the system”
• One of the antagonists was called “mama Mercury" or "mother mercy", or something similar
• The ending had a twist involving the main character’s clone as a prisoner, unfortunately I can’t remember it properly!
• "the system" (imperial government) had more than 26 letters in their official alphabet
• at one point, one of the characters enters into some sort of space gladiator contest and fairly savagely murders someone to win

The only slightly similar novel I have found was 2312, but despite the similarities I don’t think that was it.

Any clues or ideas of the book name would be much appreciated; I’ve honestly no idea what the title was, despite googling all of the above loads!