If you ever played a semi high level setons games you know that when you and your opponent go for the chill game approach it will end up in a huge t3 navy battle. with battleships pounding each other for more than 10 minutes ingame time. Also micro helps a lot as you can probably dodge 50% of the incoming damage. In combination with the simspeed slowdown late game setons navy becomes sending battleships in circles for 20minutes realtime (and cycling shields). With occasional eco management/scouting. I really don't enjoy this. And here lies the important point of this suggestion: I know a lot of people have perfected the t3 navy micro stage and some enjoy it a lot. But I also know people in the 1700+ range who share my opinion and try to avoid t3 navy all together, because they dislike the way it has to be played. What is the opinion of the majority?
The reason why t3 navy is so slow lies mostly in the slow movement speed of battle ships and the very low dps/hp of battleships. First it takes very long for a battleship to reach the front line and then it takes very long to kill another battleship. And to top it all off the power of retreat is very strong because there is a lot of mass in the reinforcment stream you can retreat into. So the frontline has to be pushed very slowly when having a superior fleet.
The best adjustment to make t3 navy more exciting would be to decrease bs hp and inrease it's dps. In current balance battleships have the lowest dps/hp of any surface naval vessel.
By increasing that ratio the killtimes between battleships would decrease and therefore decrease the time you actually have to micro your navy but making that time count more.
Bringing Battleships a bit more into the glass cannon regime would have some impact onto other units as well though. Shields would become even stronger in navyl, torpbomber more effective, bases would fall faster after a navy crush.
The perfect example for a fun navy unit is the neptune. It makes a t3 switch actually capable of winning the pond fast. As has a comparatively high dps and is fast.