You are saying that there is a long to-do list and a development plan. Than I am asking you in the name of all players of this game to postpone the development and releas of submarines and german DDs for a year, and move the game fixing and balancing to the front. Do this and the playerbase will stay and will become happy again in some time. The current state of the game was not ready for the commander rework and if you contionue to release new, unbalanced and untested lines of ships the state won't change much. Releasing the subs before fixing the state of the game will be the last nail in the coffin. And stop looking at spreadsheets and start listening to the playerbase because out feedback is far more valuable than some excell pages. Make weekly surveys after the update and read what people tell you. Sure use spreadsheets for ship nerfing because it is easier to spot a overpreforming ship (looking at FDR) than reading thousands of player writen replies.
Regarding the not enough players on test server I ask you this. What does it cost you to give a bit better reward for plying on test server? I am sure that if you make better rewards the players will come (coal or steel, special flags, small amount of doubloons. Because you see, in real life every underpaid worker will seek a better job to earn something. Just like in the PTS, why would you play if you have more profit just grinding on the live server. You are profiting from us by buying premium time, doubloons and ships and other stuff. Its time to give something back to the players.
I know commander rework can't be undone now but for next updates give it time and proper testing and use feedback from community to make it better. And ask the community if they want it in the first place.
o7