All thing being equal, new rent would be just under double. Breakeven early in yr 5 (so just over 2yrs of new rent). All gross figures.
The irony of RPZ restictions is where rooms are being let by the primary tenant for similar sums as the capped rent for the whole property. I know of one such scenario. Tenant has zero cost on this income because their landlord has primary responsibility. All tenants income is tax free too.
there are insurance implications for leaving a property vacant; its not that simple to just leave the rental property vacant. Landlord is supposed to notify the insurance company if the property is vacant for more than X number of days
I have also considered leaving our property vacant. As I have young adult children, my "plan" to get out of the RPZ zone is to rent it to them in the next few year! Realistically, if they decide to stay in Ireland, they would probably want to be based in Dublin. Once they don't need it anymore, I will review the situation.
It won't be vacant for two years, just not let for two years to comply with RTB conditions. I will stay over while door the renovations (and save thousands in the process too).
It will never be unoccupied for anything near 30 or 45 consecutive days, as stipulated in policy terms. There is also vacant home insurance available.
Your situation (in D6w) is very common. Hopefully the RPZ or caps are reviewed. I wont hold my breath.