Interesting point, I'll definitely look into it. I know the other side-effects of natures in Emerald work, like a Keen Eye Pokemon in your party increases the rate of a wild Pokemon with a held item or something (don't quote me on that one)
But whether or not Arena Trap (or Shadow Tag) works in Safari I don't know. In theory you wouldn't be able to run from Wild Wobbufet in RSE, so I'm assuming it's a no.