It is possible but kinda complex unmodded.
Wither killing device.
We can swap the septuple compressed cobblestone with any block we like and ward it via thaumcraft. Or warded glass from thaumcraft to see the wither dying
We can swap the placers with normal dispensers and droppers as botania improves these suckers.
We can swap the redstone alloy wire with automagy redcrystals.
We can swap the timer with automagy magical hourglass.
We can swap the vacuum chest with botania hopperhock.
We can automate the filling of the dispensers with red string from botania.
We can autocraft TNT with multiple solutions including botania, buildcraft, automagy.
Without mod as said the player needs to find a bedrock structure with a 2x1 hole and the wiring is far more spacious/complex.
As shown in
this design the drop can be wider than one block. That spawner has a dependancy on a mod we don't have in the modpack though, so killing with that method is not possible on a server. But it is possible to combine both wither killers