Stormborn
Explorer
Ah, player's character concept, makes perfect sense. A war injury I presume? Its a great hook for lots of games "I can help you get that back. You just need to do a little something for me." Or the player gets it back and its cursed somehow. There might even be an old patriotic spellcaster who would do it for them. As a player's character concept I don't think it deserves any penalties other than the things you obviously cannot do with a missing limb. Don't punish people for making interesting choices, but don't break the games belivability for them either. I also think in Eberron there would be lots of affordable mundane replacements that work at least as well as many modern prosthetics, and a magic item would be available by 4th level. At which point the question would be: why doesn't he want it back?