Theyre temporary threats, which is always an interesting design space to play in
As for what could be in the missing spots, 439 is missing, which is a white card between Dion and Minwu, 457 is likely a red card before Clive alphabetically, a multicolour card at 485 between The Emperor of Palamecia and Garland, 504 between Rufus and Sephiroth, and 515 between Vivi and Xande
Being in Azorius also means full access to counterspells and pillow fort enchantments to protect what you are building
Low cmc and instant speed is key here
A Reserved List Repeal Probably Wouldnt Make Legacy Cheap Enough To Cause a Significant Increase in the Player Base The most played deck in Legacy right now, Grixis Delver, requires no Reserved List cards outside of six dual lands