Possible Co-op incentive to consider:
Make it so scoring in a depositor you control yourself gives you 60% of the score for your deposit, but that depositing your score into a depositor owned by someone else gives you 80% of the score and gives the owner of the depositor 20%.
This incentivizes not only for you to co-operate with others to get more score, but incentivizes players to let others deposit.
(This is much less interesting then player made "taxes" schemes but more accessible for newer players since the taxes would be guaranteed.)