MFFS would be your best bet, since the wither can crunch thaumcraft blocks.
If you want a bedrock floor, use the quarry trick to clear out an area before setting up.
Mount some deployers on frames, and you can auto-build and kill withers as you need.
Edit- the personal safe (IC2) is indestructible to all except the owner, admin/creative and the quarry laser. 100% blast proof- though the explosion passes through so it won't contain any blasts.
Not to my knowledge, no. Imagine the fun it could cause on servers!
I'll just correct that for you