I believe public policy initiatives are already Wikimedia's second-biggest expenses, after salaries, so I don't see how that would be much more different than usual fundraising except for making it more transparent.
In 2023 (most recent year i could find a tax statement for) Wikimedia foundation had a budget of $178,588,294. They spent $92,616 of it on lobbying. That is 0.05% of their budget. So i think its pretty clear its not their second biggest expense.
