I think you're vastly underestimating how difficult it is to mine a new block on-demand.
It simply is not worth throwing that computing power at a DDOS attack. Moreover, if I _had_ that computing power, I'd rather just mine a regular block and get that sweet miner's reward.
In fact, Bitcoin Cash does have modified retargeting that drops difficulty much faster. (they could just have well dropped difficulty by 100 times at the fork, as well)
No of course not. If the tokens are useless then nobody will blame Coinbase for not supporting them. But we're talking about BCH here, which is bigger than all other coins save Bitcoin and Etherium. There's a LOT of money at stake here.
At what point do you know if it is useless or not? Who decides? How long should Coinbase wait to decide to support it..before it becomes useful or after?
I think you're vastly underestimating how difficult it is to mine a new block on-demand.
It simply is not worth throwing that computing power at a DDOS attack. Moreover, if I _had_ that computing power, I'd rather just mine a regular block and get that sweet miner's reward.