Hi all, I made a wither cage that can be made fairly early that automatically places the blocks for a wither and cages it in an area that stops it from blowing up the redstone.
The design is fairly simple and the video shows most of what is important, just a few details you may have missed:
The pistons need to be single ticked using the pulse former, they are sticky, but if they are still powered and holding on to the reinforced obsidian, they will blow up and you will have to replace them. (of course delayed by a few seconds to allow the wither to drop down)
The line going to the bottom of the pistons is to reset the trap so that the wither can still fall below.
The delays can be changed a little, however keep in mind that it is necessary to have the skulls placed a moment after the soul sand is placed, otherwise the wither won't spawn.
For demonstration purposes I used warded glass, however you can replace the entire thing with reinforced obsidian and it still works.
It can be made as soon as you have reinforced obsidian (or any other wither proof block that can be pushed with pistons), however it is a little expensive on the dark iron (you need around 110 blocks)
I have made this in survival mode also and works great, though 1 adaptation needs to be made if you cannot 1-shot the wither, this is to move the button and the red alloy wire that is closer to the bottom of the farm some distance away, as the wither skulls will blow them off the wall.
As to why I made this?
Well I wanted pipes that aren't god awful capacity wise, really that simple. Combine it with a skeleton spawner in the nether and I have as many as I want.
later, once I have a way to insta-kill the wither (still at hv on my world) I can fully automate the process to have infinite stars, though I have a feeling it won't be a problem by that point.