Burma was a cheap satellite for Japan. They only used four divisions to take it, and added a fifth later. It was the roadblock to effective supply to China and a roadblock to the British thinking about retaking Malaya, Singapore and threatening the NEI. The five divisions have been steadily holding out for the past two years. It’s a strategic keystone to the western end of their Empire, and it only cost them five divisions.
Now the Japanese decide to throw them away with the stupid invasion of India. As you pointed out, there is absolutely no logistical support for this invasion. The terrain that made it so easy to defend Burma also makes it bad as an offensive base. The Japanese divisions will starve to death at Imphal, and from that time on the Allies will have a much easier time re-occupying Burma.
And you make a good point about the starvation situation and Japan’s Indian “allies.” If the Japanese soldiers are starving, what do you think they are giving the Indians as rations? If anything, the Japanese are looking at their Indian allies as “livestock.”
Destroying this Army will finally allow the Allies to make some headway in Burma, where they had been confounded by this relatively small force for two years.