Every rank gives you the opportunity to purchase more foundry orders to my understanding. In addition, at rank 2, you get a class specific legendary quest (Titans get shotguns, Hunters get Sniper rifles, Warlocks get fusion rifles) At rank 3, you get a class specific exotic quest (Titans: Fabian Strategy (Exotic Auto Rifle), Warlock: Tlaloc (Exotic Scout Rifle), Hunter: The Ace of Spades (Exotic Hand Cannon) Beyond that, I do not know, but I suspect there are more quests and potentially more exotics that will be introduced through him. Furthermore, each wednesday gives you the opportunity to select from 3 different weapons per foundry order. For example, you order a Hakke Heja-D pulse rifle from Banshee. The following Arms Day Wednesday, your order will come in, and you may then select from 3 different variants with different perk spreads. You may then select whichever one has perks and stats that are to your liking. If you don't like any of them, select one and dismantle, because, hey, free legendary marks.