I dont anticipate Nexon even bothering to look at this idea or even try to revamp the neb system since they cant even update the crusader codex to match JMS's, but I want to put out a Reasonable Neb revamp that would be the best that we would ever possibly get.
First I think we need to clean up the Useless nebs (rank D) and special ID nebs (Greater, Lesser, Depleted) by removing the D rank nebs entirely and replacing the special ID nebs with only 1 new nebulite the "Black Chaos" nebulite that has the ability to randomly apply a "Greater, Lesser or Depleted" nebulite type stat boost, 1 for each teir, up to A rank and the stat variance can even extend to % stat boosts of all ranks up to A. nexon should also decide if they want to introduce S rank nebs and if not just remove the data for them, It's regional content exclusive data that's not getting used and so they should either embrace it and use it or remove it.
Second, we have to do something about nebulite upgrading, it's really out of place to have the upgrading of nebs revolve around 2 Cash based systems (one is not even being used currently) and one of them forces you to sacrifice nebs. Nebulite fusion needs to be updated to fit the rest of the systems that make you sacrifice for upgrading like spelltrace and starforce, by removing the neb fusion ticket system entirely and replacing it with meso cost for all fusing from C rank to A rank (or S rank) and costs would increase for the highest rank neb being fused. The cash based way to rank up will be the Reinstating of the Alien cube to the Cash shop and with it a revamp to the alien cube to work on equipment with nebs already applied as well as stand alone nebs, it will have better tier up rates than fusion.
Third, We need to fix/ replace our nebulite shop and revamp the nebulite box system. even with the drop boost that happened about a year ago, nebs are still dropping at a too low rate, so to fix this I believe having 5 ~ 6 different ranks of boxes will fix this and make the system much more pleasing to players with the other changes also applied, the 5 ~ 6 rankings being : Common, Uncommon, Rare, Super Rare and Ultra rare (with maybe a 6th box called Mega Rare if they released S rank nebs).
The common Neb box should drop from normal monsters and boss monsters at a much higher rate (like when they were first released) and should give C rank nebs at a 90% rate wile B rank nebs should have a 10% rate, because the most common ones should have the highest rate of giving the rank of lowest value. The uncommon neb box should drop from normal monsters at the rate the current neb boxes drop at and boss monsters should have it at a slightly higher drop rate, the box will give C rank Nebs at 50% and B rank nebs at 50%. Rare boxes will drop from bosses only at a rate that is either the current neb box drop rate or close to it, and will give B rank nebs at 95% and A rank nebs at 5%. Super Rare boxes will only drop from bosses at a rate a bit lower than current neb box drop rate and give B rank at 50% and A rank at 50%. Ultra rare only dropping from the hardest versions of all bosses at the same drop rate and only gives A rank nebs. If they decide to also introduce S rank nebs then Mega Rare neb box would exist and only be given from certain events and would give A rank at 50% and S rank at 50%. The nebulite shop will have the contents replaced with the Common,Uncommon, Rare and Super rare boxes, with the cost being equal to how easy they are to obtain.
Forth, bringing the fusion UI to current standards and improving the rate of rank up via fusion, this might be out of place but I feel the first 3 points are more important than this one. I think making the UI display the rank up rate of the nebulite ,similar to how Starfoce shows the success rates, would be great, It would display the Tier up rate as well as showing the % to keep the highest rank used and % to drop tier or get the lowest rank used and wouldn't also mind if they slightly improved how the fusion UI looks. I also believe fusion rank up rates need to be adjusted and improved, but since you can also fuse low tier with high tier nebs I feel we need a hybrid upgrade system for neb fusion, one where you are rewarded with a higher tier up rate when using nebs of the same rank.
With all these changes together, I believe it would make for a much more fair and better Neb system for everyone, although merchants would be upset because nebulites would be more available to everyone (and merchants are generally greedy youknowwhats)