My tastes have evolved over the years S4 has been around. I used to play with CS, PS and dagger back when S4 was back in it's seasonless form until Dark lightning came around. After a long forced break of S4 i came back around treasure hunter and still loved the CS but at the time the PS and dagger just didn't do it for me anymore so after trying out a lot of other things i came to the CS, EX and katana build.
I personally never play TD because of ST-2. I have disliked the map since the day i started S4 and played TD back when other maps were still selected, for a long time now it's been the only map people play TD on unless they want to play for the shïts and giggles.
While i agree that a ranked system is a great way to revive a game S4 is in no way ready to receive one. Many weapons are still broken and overpowered, not fun to play against and a buggy mess (St-2's TD goals still have the bugg where bombs will go through the grate when thrown for example). Before you can add a ranked system you'll need to fix the problem first before anything else.
Arena suffered from this a lot. The first few weeks arena was released it was all about what weapons you were most comfortable with and could play the best. Now it's just who wips out the breaker, fist and TB first.