Many Pokemon are currently limited to being HC-Only, and while I know it is not the intention of developers and staff to keep them there forever, while they are currently there, it becomes an ever-growing issue as more mons are added and more Pokemon get stuck there with updates taking a long time to push out.
So… how do we solve this, while keeping these Pokemon rare enough?
My proposal is Event Tokens.
Ludicolo could sell keys to access a small room where the Pokemon spawns with a 100% RR. (Think Alolan Vulpix and Alolan Sandshrew’s rooms!)
A small cave blocked off by a key area could be made and, similarly to when you first join PMU and get to select from the starters, each Pokemon is listed with warp panels behind it. Each warp panel takes you to a little room with a honey in it that will spawn the Pokemon you selected.
This means that the key never becomes outdated (as it unlocks the ability to select one of the limited mons, not one specific mon), and more individual caves do not need to be made for each limited Pokemon added, as it is one cave, and the room could be expanded to add more Pokemon if needed.
This also adds the opportunity for these Pokemon to have increased shiny rates, as well as the ability to trade the keys. Potentially even with a more expensive key option to guarantee a shiny spawn, though this would require essentially doubling the amount of rooms or making a second cave and might not be optimal.
It is not the most graceful solution, but it does give another thing to use event tokens for, and another tradeable event token item.