in my opinion,
the best way is to do like what DEL REY did with their manga translations. i mean, translate it like how the english-speeking world would say it, leave the specific jap. words like kotatsu and such alone with some explaination later on, and just be logical with the contexts and places used.
If anyone wanna subtitling, the books better be in A4 sizes cos like what some says above, they wanna the kana and kanji intact with the translation below.
this idea probbly sucks cos of the costs and such. the heck with that, cos its just an idea.