Since the existence of BCH, miners can now switch chains to mine on. Assuming they mine greedily based on price and difficulty. Can the following attack happen and how could it be mitigated:
Assuming BCH has a high market cap, in parity with BTC.
Since it take two weeks to adjust for difficulty most miners would mine BCH when bitcoin difficulty is unprofitable. Then lets say 20% of miners keep mining BTC such that the difficulty adjustment is triggered 1.5 months later and re sets to 1/5 difficulty. Then, miners would jump from BCH to BTC and mine 2 weeks worth of supply in 4 days, leave when difficulty readjusts, and BTC basically dies (because most of the time blocks are solved on average every 50mins rather than the usual 10mins, causing slow confirmation times).
How can this attack be mitigated?