I think it's good that you have a structured plan for learning as much as possible before comming to Japan. The content seems good, although i wouldn't really go for the timed plan, aka the 'chunks' of learning per months corresponding with the content.

For example by months 7-12 you will focus on phrases but will your learning from months 1-3 not get as much attention?

Maybe what could be done is, for example just say you are giving yourself an hour for learning. Why not break each hour by four 15 minute chunks and dedicate each 15 minutes for specific learning like kanji, phrases, kana etc

I think by doing this continously for months rather than dedicating so much time for one thing for a longer period it might help keep everything refreshed in your mind. Although every individual has their own way of learning and remembering, but if i myself were to do a learning plan i would like to structure it that way.

My 2cents on it anyway . How long is your planned trip to Japan?