While this would also make sense as a Barbarian title, or even a title for anyone who trains lots of weapons, I think it best fits Paladins because it refers to a professional soldier ranking just below a knight, and one who was often in the service of a knight. So since we get Knight with 190 primary armor, 22 Charisma and a horse (40th), my requirements would be 115 primary armor, 90 primary weapon, 50 secondary weapon and 15 charisma, which places it around 25th, but with a higher secondary weapon requirement justifying the "at-arms" part of the title. It also is right between Squire (10th) and Knight (40th) title-wise, so it's possible for a Knight to have a few junior paladins under him of different degrees -- perhaps a retinue made up of a page, a squire and a man-at-arms. And of course women would be known as women-at-arms. What do you think?
~Thilan