Func has it right, that C-Sub paper is super old and makes alot of bad assumptions….it needs an edit. Obviously if Japan drops absolutely everything to deal with India than the Russians should help out. In any case, if the Japs put everything into a J3 attack and lose some planes to the aa then sometimes the Russians can simply liberate it and UK can build there on the same turn.
I’m not really big on India for the reasons outlined above–it ties down valuable hardware in an area of secondary strategic value, and if Japan plays it right UK is forced into a defensive posture there. Still, it is fun to play and every good A&A player should give it a try–just preferably not against your toughest adversary.
These days I hardly buy any UK factories unless its late game and UK has the cash to spare…but if you are going to go with a factory UK1 then India is probably the most interesting option.