Looks like NRIs in Kerala might be able to exchange old notes with the RBI, in their own state, soon.
Like I had mentioned earlier, for NRIs in certain states, it was best to not exchange old notes than travel to other places because they would end up spending more than what they would get back.
With such problems arising, the Bank Employees Federation of India has urged the RBI to open special centers in Kerala, owing to it's high population of NRIs. (Source)
What this means is that, if the special RBI centers are open in Kerala, like in say Kochi, where there already is an RBI center, then NRIs in Kerala will be able to get their old notes exchanged without having to go to other states.
I'm hoping this request is sanctioned by RBI. Let's wait and watch.