The main one is to put the Redstone mechanics from Java Edition directly into Bedrock Edition (maybe including quasi-connectivity?) while keeping things like movable tile entities (chests, furnaces, etc...) because I think that would allow for faster and more compact contraptions that are available in Java Edition, but not in Bedrock Edition. The next one is allowing you to put other items in your off-hand besides shields because it would be a nice quality of life change.
I only joined PMC late this September, but it was a decision I'm happy with. Seeing what kind of community this place is is really cool to see. All of these people being creative and sharing the things they enjoy making is not only impressive, but encouraging. I know, at least for me, that I have been able to see what others have done and make my work better from it. Happy Birthday PMC!