83 shiny Pokémon, 7 gold cards from GX Ultra Shiny.
Several full art supporters and stadiums from various sets.
Some promos.
Some cards from "Remix Bout"
You already mentioned some advantages and disadvantages about having that in "Hidden Fates".
It's still not the best, but I would go for putting the shiny Pokémon, gold cards, "Remix Bout" cards and promos in "Hidden Fates", and the FAs in a collection box for collectors as A cards.
But if you make 10 collection boxes with 2-4 boosters and have that many secret rare cards to collect, at normal ratios, you'd need to buy 100s of boxes, that's not only a lot of money, but also so much waste (plastic, cardboard, packaging, extra fuel spent on shipping etc.). When the Generations boxes came out the trend started and people bought stacks of boxes just to complete the set and it has not become much better since then. Even the card stores throw away the boxes to sell booster individually.
It might not be the best way to make money for the Pokémon company, but the best would be to just make a booster box (can be less than 36 packs, less than 10 cards per booster and more expensive) with a shiny card in every pack.