Using iControl to change pool members on ASM

Absolutely you can do that with iControl. Look at the LocalLB::Pool interface for the following methods:

struct IPPortDefinition {
  String address;
  long port;
};
IPPortDefinition[][] LocalLB::Pool::get_member(
    in String[] pool_names
);
void LocalLB::Pool::add_member(
    in String[] pool_names,
    in IPPortDefinition[][] members
);
void remove_member(
    in String[] LocalLB::Pool::pool_names,
    in IPPortDefinition[][] members
);

You can query the pool members with the get_member() method, add members with add_member(), and remove members with remove_member()

You'll just have to build the logic into your application to make these calls when you update your DNS alias changes.