Weapons are just the basics: melee weapons, pistol, smg, shotgun, rifle, sniper rifle, assault rifle, and there are no upgrades. While it is possible to play completely as an action game, it is intended that weapons are just one of the tools you have for completing objectives.
As far as items, there are a few, and they're usually specific to a certain mission. At most each character is going to be carrying two weapons plus an extra item in some missions. Each agent has their abilities built in, so the agent that can pick locks does not need an item in order to pick locks.
Health can't be restored during a mission. When an agent dies you can call in a replacement agent. There is no health bar, but when an agent is injured their video feed will become more distorted like an old VHS tape.
Characters do not improve from mission to mission, though you gain access to more agents as the missions progress. It is common for agents to die during the missions and be replaced and we didn't want players to feel like the had to reload the game in order to keep their agent's stats.
Currently you must remap keys manually in a config file, but a patch should be available on Monday that will add this a keymapping menu in-game.

Thanks for the info. :)