Board Game Arena

OK - I don't know if this has been asked but the arena points gain/loss is based on the ELO gain/lost. So what is to stop someone from playing simple games and conceding to artificially lowering their ELO, switch to Arena and maximize points gain and minimize points loss? Repeat when their ELO gets too high and then make it to top of the arena?

No, there are two totally separate Elo scores now. All time Elo, which is affected both simple and Arena games, and Arena Elo, which is affected by Arena games. Arena Elo change is calculated based on Arena Elo, so it has nothing to do with all time Elo. Of course, they tend to be quite similar.