That isn't modding. Save Editing is totally different.
It all depends how loose your definition of the term modding is. With such a wide array of console commands, a user can mod their save to do a number of surprising things, like turn dungeons into full homes and such. That seems like a modification to me.
What you cannot do is the type of modding PC users can, you cannot create new References in the world. No new homes, spells, scripts, quests, etc. etc. are possible. You are stuck with only console commands, which may be diverse but are much much much more limited in scope than a simple .esp mod can do.
Just a warning I'm always intrepid of adding spells that were removed by Bethesda. Sure it might work when you first try it but there might be some kind of critical bug with it that causes bethesda to pull it in the first place. For example it might hurt your followers whenever you use it or it might cause everyone to be aggressive to you (including followers). I have found that aoe cloak abilities are riddled with bugs.
As long as it doesn't have the Hostile box ticked in the spell effect window, it will not hurt friendlies. I don't think bugs had too much to do with this. It was probably much more likely it didn't fit their idea of what they wanted vampires to be.An invisibility spell combined with a frost cloak would've, functionally, worked like the Volkihar grabbing at a victim from beneath a frozen lake.
I always felt that the new Death Grip spell available to VLs was the representation of that power. Being able to svck people towards you then throw them about seems to match that described power spot on. How else are you going to simulate reaching through Ice to grab someone? How many opportunities does the player have to look up through Ice?What would happen if you were already face to face with a Vampire that could pull you through a wall? My guess, it could pull you toward it. And we can already do just that. It seems perfectly fit already.