I've never seen anything like that, I think its a limitation of the game engine other wise we probably would have seen a mod like that already.
While its not exactly what you ask for I recommend.
JIP Companions Command and Control by jazzisparis
http://www.nexusmods.com/newvegas/mods/50468/?tab=3&navtag=http%3A%2F%2Fwww.nexusmods.com%2Fnewvegas%2Fajax%2Fmodimages%2F%3Fuser%3D0%26id%3D50468%26gid%3D130
Not only allows you to have unlimited companions but you can also command them to specific point and them guard it, so for example you could have Boone on top of hill while you go out and lure enemies back in for him to snipe.