I just finished Chris' campaign yesterday, but I missed a few Serpent Emblems. Obviously I need to use Piers to get some of them. So if use use Piers and then switch back to Chris later, will Chris still have all of his weapons?
"How many people here have telekinetic powers? Raise my hand." - Emo Philips "I live on a one-way dead-end street." - Steven Wright
I believe so yes, since you'll be doing a Chapter Select to continue that campaign with Chris you get the weapons you finished the game with back. Ammo, grenades, and health will be based on what you last saved with if I'm not mistaken.
Just finish the campaign with Piers though, it's pretty awesome playing through with each character. That way anytime you play in the future you'll have all the weapons for both characters on all campaigns.
http://s1227.photobucket.com/albums/ee424/ehsteve12/ My Legend of Zelda Collection - Last update Nov. 1/12