My MT is French, but I love all local accents, or at least I find them fascinating. And the grammar is often linked to the old local languages, oft brought in by invading tribes in the past. I used to live on the Danelaw border, and you could notice the influence of Saxon and Dane in local speech.
I lived in The Potteries, and got on much better with local accents than Surrey/London flat RP OH. And we then lived in Leicestershire, and same again.
I helped with a group of local people in the Estate near us- and I had no issue with the was/were- it was part of the people and the way they were brought up, and accepted as such, with grace and humour. One old guy was married to my French friend. She arrived in the UK to marry him when she was 55, with not a word of French. She learnt with him and his friends, all lovely people, and she uses the was/were inversion- which is hilarious.