Wasn't leg theory just balls bowled around leg stump with a leg-trap field - the opposite to the current tactic of bowling around off stump with most of the fielders on the off side? It turned into fast leg theory/bodyline when you got quicker guys to bowl only bouncers; rather than bowlers just bowling leg side lines.
It would be an interesting thing to try regular leg theory in the game though - see if it would work as it did IRL (very boring, grinding cricket with low run rates and no real chances to take wickets is how I've seen it described...) - I'd imagine that bodyline would be harder, but probably more effective...