Some great ideas. I takes a lot of work and need someone who has the motivation. We appreciate that you are here trying to take this to the next level even if some of us are a little absent from time to time. The reality however is that we all have to keep food on the table and hive does not do that just yet so we might be tapping in and out as we have more free time.

Some ideas to think about.

• @derangedvisions has run great contests over the years and one tool that helps to increase engagement is to have a "pro" category and a " amateur" category. This gives people who are starting out in photography some hope they might win a prize. Something to think about so it does not just become the same people week in week out winning at pro level while the base of users don't bother to enter if they don't think they will be competitive.
• The above idea raises more complexity with voting however, but people can vote more than once if they like to cover both categories. You could also have an editors choice along with the popular vote, and get guest editors to vote each week if its too much work.
• Historically a lot of people like the raw editing contests, @photogames used to run them and different people entered them. There are people who don't have the chance to travel or get out as much as some of us and don't have the raw backlog to work with so it engaged a different base.
• I think you could take a lot of ideas from @photogames which has been inactive since 2018. It was a @jarvie and co run activity, they had high engagement when it ran, but it does take quite a bit of work and planning and eventually people running it burn out (or move onto those pesky things which pay the bills). Simple games like guess the shutter speed were simple for people to engage with. They would have more active games where people had to go out and shoot something on request, but you need a really active community to pull that off successfully.
• If you want to force the issue with people posting to the community you could make it an eligibility requirement to post to the community to be featured in the photofeed daily roundup. But that is somewhat limiting and might reduce the quality of the roundup. So I would keep the daily post as a marketing tool and draw from the whole of hive. You could however require people participating in the competitions post there entry to the community and put a link to it in the comments that people can vote against?