Unexpectedly named by Queen, one changing for the better?

• Constitution modifier, e.g
• Change maker
• One changing a bill
• Person who makes change
• One improving in the morning, one coming last
• Editor, in a way
• Copyreader, e.g.
• Bill modifier, e.g
• Revisionist

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
Amender \A*mend"er\, n. One who amends.