@Dusty : I can't help but feeling that your assessment of the chances of a 10-block rewrite are bit unrealistic.
https://bitinfocharts.com/
Bitcoin Cash (BCH) hashrate at ~2.5Eh/s is currently around 1/8 of BTC. That's not really "tiny"!
This could of course change... but to rewrite 10 blocks successfully you'd need to wait quite a long time unless you have significantly more hashpower than the overt BCH network.
To "borrow a few pools" to rewrite 10 blocks on BCH, you need to produce significantly more than 51% of its hashrate. If you can have 51% your chance of eventual rewrite even of 10 blocks is guaranteed, but the closer the hashrate ratio the longer it will take and others will notice.
So you would need to overwhelm the honest BCH miners with a hashrate multiple times theirs, to pull it off fast. But here's the rub :
The set of BCH honest miners are likely from a subset of BTC honest miners which control ~50% of BTC hashrate (or more). We have seen this in the past when BCH mining hashrate equalized with BTC hashrate during times of "crisis" (times where hard fork upgrades needed to be secured/defended), such as around Nov 13 hardfork.
https://bitinfocharts.com/comparison/hashrate-btc-bch.html#6m
It's rational to assume that once a 51% attack on BCH is detected, the honest BTC miners will again defend, and there is no way to secure an overwhelming hashrate majority against them.
This is why I'm confident that a 51% / chain rewrite attack is purely hypothetical given today's Bitcoin / Bitcoin Cash mining relations.
https://bitcoil.co.il/Doublespend.pdf