Nite69, I think you're fixing a difficulty freeze hole - it's possible to spike difficulty up to an unlimited value if you have the following pattern
Block time A
Block time B (much larger than A)
... Many Blocks with time < B ...
Block time B + dx

Difficulty is raised by a factor of (found blocks * target time per block / dx). Now you need 70(ish) blocks in the middle, not sure how far forward you can stick a time stamp, but you don't need to be the source of those 72 blocks. e.g. you could predict when a multipool was about to hit and then try to set your attack block B. Finally, you close with the B + dx, a microsecond (or less) after B, and can start trying at any time after there are enough in the middle.

I'd like a difficulty 21 billion times higher, kkthx. Although, I'd say you're only limiting it to 21,000 times higher, or 73 days for the next block, if such an attack is performed, so I'm not convinced if this is what you were going for after all.