In your scenario they would need a huge amount of hashing power to actually make their own giant blocks
I guess you only need to construct such a specific block that takes forever to verify, not necessary a valid mined block, no hash power is needed
An economically rational miner wouldn't sit there trying to validate an invalid block forever... they won't stay a miner for long. They'll set their own limits and seek the longest chain of valid POW. They already mine short coinbase only blocks simply due to fear of orphan risk.
If you look at the coinwallet.eu September attack, they did not do anything, just give out coins that stored in millions of dust addresses, and people automatically come to construct special transactions to claim those coins. This is similar to throwing out millions of $20 notes from the top of Empire State Building, it will immediately jam the traffic of Manhattan. How do you prevent people from claiming those notes? In fact F2pool is the one who claimed a mass of those coins and get a block took 30 seconds to verify
F2Pool did that block to clean it up. I guess there is always the obscurity option for attack resilience.