The Gateways to Eternity mod was designed with mod pack developers in mind, and I have been able to successfully get it to spawn Pixelmon loot from special loot tables. It's also capable of running commands, which would potentially allow it to summon pokemon, and/or legendary pokemon. However, I think the primary use I'm going to have for it is in producing vouchers/collectables of some kind, which then can be exchanged for the Lustrous, Adamant, and Griseous Orbs.

So far there are 11 pearls, and 7 Symbols from Frontier Brains. This almost perfectly allows me to add 7 vouchers of which 1 each must be collected, and 3 vouchers unique to each orb. However, there is one voucher left over. I might decide that the best use of that is to generate a random plate, helping with the Arceus quest.

Now it's time for the tedious task of adding in all the new loot to the datapacks and connecting the appropriate quests to make the vouchers work.

They've been added, but I haven't tested each and every one to make sure they work