that will be interesting: how you will be able to open the nxt-links without having to trust anybody, without any utilities or plugins
Non-Nxt users have to trust Nxt bootstrapping nodes (but they won't notice this). Nxt user can use their own Nxt client to resolve links.
and how you will prevent someone registering the same name (or allow to change the old names values)
Once someone registers a domain name noone else will be able to use the name to reassign the address. The network will ignore all such attempts.