Hi there to Ireland. It is really a pitty that Ireland is not really for Liners. I have been there some times, but only by car and for business.
Back to your topic. I believe the easiest way would be to find a "best buddy" here in Germany who can register your Liner under his own name. You keep the car documents as the proof of ownership and pay for taxes and insurance. So with this you can "hire" the Liner when you want to travel. I know that in many baltic countries it is very commen to do so. They bring the car back to hometown even. If you go to e.g. Rumania, you will see many cars with German number plate.
I don´t know if this is legal or not, but I it must be somehow as I have seen the proof many times.