PowerAuras I understand is implementing the new blizzard auras, so I think could replicate that sound effect should you wish with the new graphics.
All you would need is the sound file, and if needbe convert it since wow no longer supports playing wav files, which many addons used.
A decent action bar addon will allow you to have bars visible based on a stance, so you should be able to have one visible only when in meta.
Dominos or Bartender should be able to do that.
LunarSphere is probably what you'd be looking for. It is based off the Necrosis model but is universal and can be used by all classes. You can customize all the buttons and even use them to make collapse-able menus for spell stones, summons, rituals, etc. LunarSphere has lots of built in button assignments for summoning random mounts, using health/mana pots, food/drink, etc. And all buttons support left/right click options so you can effectively cut your buttons in half. (I put cooking on one button: left click for cooking, right click for campfire. No macro needed) I use Bartender for my main action bar (and it pages when entering meta or switching specs) I like to have my main bar in the middle of the screen to watch cooldowns and rotations. But I use LunarSphere for all my other buttons. I suggest you check it out as it is quite the add on
like others have said, for me necrosis was and is an integral part of being a warlock. Yes we may have lost the functionality of our shards and stones etc, but we still have 3 shards. Tbh even if necrosis tracked those 3 I would be fine with it, I liked having all my ritual spells on it as well as fel armor and healthstones (had make/use healthstones bound to e).
It is being worked on as we speak, let us cross our fingers for a quick and healthy necrosis!