IDK if this has been thought of, but I got an idea while playing Emerald today.
Ever find that one Pokémon you've been searching for? Coincidentally find a shiny? Did it just run away and piss you off? Well piss no longer, after a Pokémon flees, some nearby grass rustles around, it's the Pokémon that just fled! But warning, every time it flees, it gets further away, and using repel will prevent it from appearing, and you indeed can find Pokémon on your way to it, but it won't be there after you encounter a different Pokémon.
So with that, it can be less annoying, but still have it's Safari Zone annoyingness in there somewhere.
this would have made getting Chansey far too easy in RBY
That's why it's a new idea rather than an old idea, for future games not past games.
durp
but aside from that, it is workable, just as long as they don't make Safari Zone Pokemon too OP