Actions: Sadly this would require a large update, which they cannot do without the coding from Kovu.
Emotes: You can already make custom emotes. Why not make some yourself and release them as a custom pack?
More maps would be possible, and would be good. Red has attempted this with his map pack, which you can install easily. I do think the most recent map updates were just pure lazy, especially south pole, and that's the reason nobody uses them.
Rules button: Sadly, I think this would require Kovu again.
More models: Again, Kovu's coding needed.
Customization abilities: Once again, coding. You can make presets though.