About Melissia server, it's actually even easier.
You don't need to run Meta Injector every time you login.
After the game is updated (you can click "play" in the launcher), make a backup copy of pad00000.meta to your desktop (or any other folder).
This will be the "regular pad00000".
Then, run Meta Injector and, when it is done, make a backup copy of the new pad00000.meta (to any other folder).
This will be your "injected pad00000".
Always keep the "regular pad00000" in the Paz folder before you click the launcher exe.
Then, before clicking "play" in the launcher, overwrite the "regular pad00000" with the "injected pad00000".
Now you can enjoy the game with mods :)
Also, some hours ago someone asked in the public discord if nude mods were allowed.
Fortunately the comment was deleted but please, don't be stupid and use common sense.
Writing it here so it does not happen again.
This is something that is definitely better off being left in the shadows.
Additionally, if you use search in the server, you can see a former CM stating that visual changes (nothing that affects gameplay) are ok.
However, if you keep raising the topic, the Admin might block mods and you spoil everyone's else fun.
Finally, the "Now processing" thing has been happening the last few days and the Admin is fixing it.
Doesn't happen often, but it is there.
For now, keep trying and use "connect to random server" and it eventually lets you in.