What health insurer are you currently with?
Quinn have a plan called
HealthProtect that lets people "protect" their previously served waiting periods if they have to cancel, and it costs €65 per annum.
There's also another thread on the forum where a VHI member says VHI will let customers move to [broken link removed] to do the same, and that costs around €82.
Both insurers are primarily offering these plans to customers who are experiencing financial difficulties, which isn't what you're going through, but they may let you switch plans if you ask.
Two things to point out are that i) conditions that develop while you've downgraded your cover will be subject to at least a 2 year waiting period when you upgrade your cover in the future, and ii) as you will (presumably) be out of the country for more than 6 months in the year, they're not obliged to let you move to these plans.
There's nothing you can do on the first point, but ask anyway about the second point. They may be more flexible in your case as neither plan offers an iota of cover while abroad, so they have no potential claims exposure.
I'm not sure if Aviva offers a similar product, but if you're a member with them, give them a shout and they'll quickly tell you if there is or not.