Yes, it can work. I know somebody who used to run a horse feed co-op for similar reasons.
Also, we've just started buying poultry grain by the 'big bag' (600kg a time), which gives a substantial saving over buying by the sackful. That said, if I was buying the big bag and distributing the contents in sacks to local smallholders, I very much doubt that the saving would be worth all the effort involved.
Whereabouts are you Southmains?