Well, this is a fine idea, just that we already have this implemented far as i know, in the gun runner Fortress there is almost always a constant amount of caps, namely 19k
there they get it from people paying for proffesions/mercs/bases/cars
its the same in ncr shops isnt it? money gets devided acrosrs vendors
if the gm's or the game it self will simply generate money one could argue that it will distort the economy and allow players to become rich very fast, personally i think that money gets thrown in to the game anyways from quests, box hauling and shit shoveling in the infinity,the longer the game world goes, the more caps it contains in total