Robert,
I have a friend he was born in UK with a parent born in Eire. He has a house in Ireland and has a Filipino wife who has Residencia status in Spain..

They have been to Eire a few times. They obtained a visa free, by postal applications. Never had any problems extending when in Ireland.
They are now in effect living in Ireland, and his wife has Irish Residencia status.

I have dual nationality British and Irish. I have never worked in Spain etc. only UK. I recently took my Filipino wife to Gibraltar. I used my Irish passport and she was permitted entry, showing her passport and Residencia Card, without any problems.

If I had used my UK passport, or had declared I had dual Nationality, she would have needed a visa.

I understand I can take my wife to UK using the same MO, but I would have to conceal my British Nationality and or lie about it.

I am thinking of renouncing my British Nationality, and then I will be able legally to take my wife to UK without her needing a Visa.