Current Behavior

Once all Gigantamax Pokemon are unlocked, the Max Raids become essentially useless, outside of a secret achievement. In addition, once all Gigantamax Pokemon are caught, all 34 of them have even odds to be encountered as a boss in the Max Lair.

Improved Behavior

Once all Gigantamax Pokemon have been caught, encountering a Pokemon in a Max Raid will notably increase the odds of that Pokemon being selected as the boss Pokemon in the Max Lair (maybe set to a weight of 5?) until either a new Max Raid is defeated, or until the Max Raids reset at midnight.

Reason for change

Gives the Max Raids a reason to persist in the late game, and decreases the amount of randomness needed to resist all Gigantamax Pokemon, without removing it entirely.

Detailed Description

As there are only 10 Max Raids available each day, this does mean that a player wouldn't be able to ensure the Pokemon they're looking for will get the boost each day. In addition, Melmetal, both Urshifu and Eternatus do not appear as Max Raids. I feel like this does enough to ensure that the randomness of the Max Lair isn't completely removed, but is somewhat tempered.

As far as I'm aware, other than the Max Lair, no dungeon has more than 7 bosses at a time. By setting one Pokemon's weight to 5, you still end up with a less likely chance to encounter that specific pokemon than with any other dungeon in the game.