Buying Attachments

I think it be really cool idea if you were able to buy attachments for your weapons. You buy the base gun and it gives you like a second menu for attachments showing the stats of your gun like damage, accuracy, extra... and maybe later on the road there can be DLC for more attachments and weapons. I think with all that in the game it would really expand out the options and advantages against the monsters. And maybe different types of ammunition you can use like the firebug can use incendiary ammo, commandos can use armor piercing for the Flesh Pounders.