One thing I saw on another game (don't want to game name here) and I really liked was this one:

- there was a list of "development plans" and the developers worked on them as they had time
- yet there was the possibility for players to "donate" / "pay" for having a certain feature implemented earlier or a problem treated as priority
- things worked like this: the developers estimated how many hours a feature would request, put a price per hour of development (let's say $20) then start accepting donations; once the full amount (let's say 30 hours * $20 = $600) were collected that feature become a top priority and was seen going live in maximum one week time
- people could not propose new development directions, just donate for one of the existing (planned) ones so they give it a higher priority

This way:
- the developer could earn some extra money (which could eventually use to extend the team, at least with part-time / project-base workers)
- players would become a decision factor on what things should be developed first (what they consider more important)
- everyone could see that new features are actively implemented (because otherwise for example maybe you work on a huge update that takes 600 hours of work, but during all this time players won't see any change and could thing that you're just hanging out on a beach in Hawai).