He thinks of the PoW-Coin as totally independent of NXT.
But that PoW-Coin should bridge the layers. Nodes have to prove that they keep the NXT blockchain online and therefore securing the network.
The NXTcoins will be making NXT API calls, otherwise you cant mine them, or trade them
Not sure, I got that.
NXTcoins will make NXT API calls on behalf of whom? And which one specifically?
I can think of several reasons, one example is if the coin needs to receive data via AM. It would then have to be part of the NXT network to be able to get the AM data.
Another reason that is just for security reason is to verify the total number of coins in circulation. It needs to match the total mined. until we get multisig in NXT, there is the possibility that the accounts that are holding the issued but unreleased coins will release some extra, especially when there is a nice market to sell it to. Since there is nothing I can think of that will stop that, the plan is for all the nodes to actively reconcile the total balances and if it doesnt add up properly, alarms and a snapshot of the current account balances are made. Then if the problem cant be resolved, everybody simply redeems their snapshot balance for a replacement Asset, and resumes without any real harm done.
The only harm would come to the one who broke the trust by trying to sell off what they were supposed to only release to the miners. Whatever coins they were able to pilfer wont be worth that much since it will be obsolete. Also, I think we can have part of the alarms to be canceling any outstanding orders the miners had on the AE. Anybody that is trading in these NXTcoins is advised to be running the alarm bot. So not elegant, but I think practical solution to not be able to create coins only when they are mined.
You can imagine how elaborate all this will be, all requiring access to the latest block. NXTcoin miners will secure the NXT network, I am pretty sure of this.
James