The forking defence would work if there were more established decentralized exchanges based on atomic cross swaps. The reality nowadays is that centralized exchanges have a big say about forks. It would also be a challenge to exchange from scammycoin to vertcoin2 because of replay attacks.
Yes, there need to be free and open exchanges so both coins can be traded. This infrastructure is still missing, but I am optimistic for the future. Right now exchanges have a lot of power and will likely not care about small coins such as vertcoin.
Replay attacks can be solved from from one side by adding a command that checks if there is a valid checkpoint. Then coins can be split and in principle there is no more problem trading them against each other.
You're right. There is not a free market if exchanges choose which coins to list. This is also a big caveat in bitcoin's ETFs and derivatives.