I
think I get what you're trying to portray in that drawing, and you're definitely going to need the Mechanic. I've never seen a randomly generated structure that's perfectly set up for 2 traps and a heart statue. If you find something like that, you might as well go out and buy the lottery for such convenient world gen. However, there's an easier way to do an AFK farm. If you look to
this video of a fully automated expert world playthrough, his invulnerability machine involves taking 1 point of fall damage and continuing to do that to stay invincible. He uses teleporters, but I believe you can just hoik back. With each hoik taking 1 tick, and invulnerability time being 20 ticks (I might be wrong on this number, but if I'm wrong, the invulnerability time would be 40 ticks, which is better because you have more leeway with your machine), you can just barely go through a loop. Knowing this, you could make it using a wrench, wires, pressure plates, a hammer, a couple blocks, honey, a heart lantern, and a heart statue. All available pre-hardmode and safer than just hoiking in a circle. You only need ~20 defense to actually survive in this machine, an amount you should have by the time you beat Skeletron, and a small price to pay for invincibility. With this invincibility machine set up, you can go buck wild with traps and using some more hoiks, you can bring enemies into a trap room. This invincibility machine isn't made with loot collection in mind, so you'll need to add a final hoik for moving the items towards you. All together, I don't know the items you'll need since it's all variable based on how large your scale is, but it's definitely possible pre-hardmode. This setup would be more useful past pre-hardmode and into hardmode since invincibility doesn't have diminishing returns with the difficulty raise and since you just get more powerful traps to AFK with.
