So I tested if turtles would be asploded by the wither. Turns out that they don't get blown up. With MFFS and a little rednet I can foresee an interesting method of auto wither slaying. Was this known already?
If the wither can still see you (or anything else to kill) it will stay on the regular blocks.
If it can't see you, it will change to the blue death shots. Those blow up anything, including turtles (because they are blocks).
The ceiling of the Nether is bedrock. Build a room there and place a sticky piston with one block on it so that you can lift the wither into the bedrock ceiling. Activate the wither and then the piston and he's trapped. Attack manually or with a turtle. No need for fancy blocks, MFFS, or anything.
Downside, Ult has a flat bedrock mod.
That includes warded stuff?
If it has a target in sight, it will happily "phase" through warded blocks. In reality, it momentarily destroys them and moves within the block's hitbox allowing the wither to simply walk through it. Currently MFFS is the only thing that actively pushes the wither back into the containment field, afik.
Oh, thanks, now i can stop making warded stuff.