I think holding more helium in a smaller space is the opposite of what you want. The lifting force is equal to the weight of the air being displaced, so you want as little stuff as possible in as big a volume as possible.
Maybe if you went the other way round and compressed the atmosphere?
I’ll just compress more helium and make the balloon metal so its stronger and holds more in a smaller space
I think holding more helium in a smaller space is the opposite of what you want. The lifting force is equal to the weight of the air being displaced, so you want as little stuff as possible in as big a volume as possible.
Maybe if you went the other way round and compressed the atmosphere?