I don't really see why not.
The only one I've never thrown into the mix is the ephedrine but I've done weed,Klonopin,caffeine and Dexadrine and dex is probably as strong or stronger than ephedrine.
The ONE problem I'd be aware of is that both ephedrine and caffeine raise your heart rate and weed can cause panic so too much ephedrine in particular with the caffeine and weed could be a panic attack in the making or cause racing heart/tachycardia.
You'd PROBABLY be ok but I'd probably leave out the ephedrine if I were you.
On the other hand, the benzo can help out with the racing heart/panic, so that might smooth things out.
Overall, it shouldn't be dangerous, but just don't overdo the ephedrine and caffeine or your might get more stimulation than you bargained for...