CCS_Covenant | 1.14.3 Shulker wither cage @ccs_covenant5823 | Uploaded 5 years ago | Updated 1 hour ago
it pass 24 hour tick warp test (in about 300tps which means 360hour real life) while loaded.
but failed during reloading test(tp player in order to load/unload chunk every 400gt), it fail after about 4-6 hour in a very strange way. i guess it because of collision algorithm change in 1.14.3

boat is important and minecart is important
becuase those things help alignment shulker
boat will make sure that shulker can't attack wither or other player
or other shulker

snow golem is important, it will become main target of wither
and prevent 0.1% change of blue skull since wither's main head can't
'see' it.

it don't work before 1.14.3 because wither only take entity who can be seen by their mian head as their target before, and it changed in 1.14.3.

it's very expensive and not perfect since it's not 100% reloading proof, but still a potential cage design