This has been suggested before. I've also seen this idea in the form of a Battle Pass, which has different seasons with tiers and rewards to unlock.
About the cosmetics; the simple conclusion to this is that it won't really work on a Minecraft server. The amount of rewards you can give are very limited, as there is not much variation possible. If you get a different trail or win effect or other vanity item every time you level up, there will be just too many items to be made so many will look very similar. There are no big possibilities on Minecraft to do this. There will be no excitement in unlocking a new rank as the reward won't be so much cooler than the last one you unlocked.
About the flight in lobbies; on the Java network this already excists (for Emerald rank or higher). I don't think it is on Bedrock yet, but if it was added that should be for high tier donators as well, not by leveling up in my opinion.
About the ranked mode; this has been suggested a lot as well and I'm not sure about this. On Java I don't see this happening as the playerbase is too small for it. Maybe on Bedrock it can be implemented at some point, but you should explain in more detail how you'd like to see it.