This post would belong best in the market discussion section rather than here, this section is for botting.
Anyways, all of the big gold traders really just do straight trades, nothing special, and still don't end up with many/any bans at all. If you wish to be safer than that on F2P there really isn't a way to do imbalanced trade, but for P2P you could duel it over or any other unsafe mini game. If you wish in F2P the receiver of the GP could offer some junk or you two could make up some story, but most of the time GP trades are quite safe.
Every now and then though Jagex sometimes beefs up their RWT watching but usually this only hits a few people and doesn't last for long.