I remember Conker's being quite streamlined back when I played it, pretty much all of the money was mandatory. Is that really the case? How about the order of events, do you have to follow the one route from start to finish or can you tackle some levels in any order?
you dont have to get every money in the game (though you do need most of it, like 90% probably), and you can do things somewhat out of order for the first half of the game, like fighting the GMP before going to the vault, or vice versa. By the midway point of the game though it becomes much more straight forward --- http://www.gamefaqs.com/sg1000/916314-dragon-wang
I think you can do Bats Tower after a certain point in Barn Boys, likewise I don't think there's anything stopping you from doing Sloprano once get access to the hut (But you need a certain amount of cash for the portion afterwards for the "toll". The main obstacle is paying Mr Barrel who initiates the last half/third of the game.