When japan had zetas “accidentally for 2 years” in its gotcha packs (in game called step up) they were stupid expensive. Guaranteed to drop 10 zetas if you went through all these step ups at incremental crystal costs startling attempt 2299 crystals most of them pack was gear ( fantastic gear) all the way through the packs but to get to the zetas was pretty much $100 usd but you got loads of gear and zetas and omegas. Was a fantastic pack. But once the community found out about it cg killed the zetas in it immediately. Japan still gets way better packs then the rest of the word to this day but nothing like the step up pack.
I say this to say it's a really bad idea to introduce zetas in packs by the time i could even use the zetas i had over 100 just from the step up packs. It would cause a huge imbalance in the game and the mod in balance is bad enough no need to introduce another one. Imo