It ideally needs to be automated and enforceable which is difficult.
Isnt there always an incentive for the pool operator to lower their fees in order to attract miners. We have three pools at the moment, even if we got all of them to agree to the increase in fees with half going to dev to fund the project, nothing is stopping some1 else from starting their own pool with a lower fee. Maybe thats not an issue right now, but it will be if we rely solely on increasing pool fees to support the project.
I can mine monero on a pool with lower fee that does not donate to core devs, but I choose not to, same with this project, more pools are more than welcomed even those that have no fee, means the network is more decentralized and less prone to attacks, people who believe in the project and understand that core devs need funding to make things happen will mine on such pools and gladly donate small part of their hash rate for the project.