Let’s say you have 100k or more and would want to own a stake pool. You may not have the tech skills or the time to actually do that though. An alternative would be to become an secondary owner of an already existing pool. The pool would benefit because your 100k could be added to the pledge and hence (depending on the effect of a0) would increase rewards for everyone.
You would have a benefit too, because as an owner you would likely get a share of the pool’s fix and its margin. This can be considerable - see the difference in operator return and delegator return for any pool of your choice.
However, that share of pool margin is not an automatic thing, it would need to be negotiated among the already existing owners. There needs to be sufficient trust among the owners, because there is only a single rewards address for the pool i.e. those rewards must be distributed manually among the owners. In future, this can be a plutus script address, such that extra distribution can be done by a smart contract. The latter is something I’m already working on, so that in the near future that contract can not only distribute extra rewards to loyal delegators but also to partners who may want to become co-owners.