You can always phonetically spell in the dialect. Which Finnish does often. So if you have a dialect you write it out phonetically. There might be slight deviation from standard phonetics(some vowel variations), but the dialect does get rather close.

In the end, maybe it is inherently wrong take that same word in different dialects is the same word. Usually they are close enough to be relatively intelligible.

Unless each spoken dialect corresponds to a matching written dialect. But that just sounds like an even messier system than modern english.