So my dad and I were talking about the mob vote and the mountain biome. We came up with this: Say the glowsquid wins the mob vote and gets updated with mountains and caves.
Mountains gives a higher build limit, say 800 or 1000 blocks. The whole world gets taller to maybe 4 or 5 hundred blocks average, allowing space for elaborate and huge caves.
This also allows bigger oceans, so the squid brings with it bigger oceans. Deep, dark, and has a few glowing critters here and there. Of course, riptide tridents are sometimes difficult to get, and you'd need an awful lot of water breathing potions, as the deeper you go now, the slower you move. There could be somewhat rare structures that give you something to swim faster.
Deeper oceans would bring bigger and more elaborate underwater structures. But they'd be rare, as would the deep sea. But it would be worth finding for the loot.
The caves get their own biomes, and their own sometimes glowing creatures and monsters. You have huge, open areas with holes to the surface letting in some plants with them hanging around the edges. Massive stalactites with rare ores hold it up. Or even small maze-like cave systems full of glowing plants and animals. Long underground rivers leading out to deep oceans.
Also, bigger and better underground structures. Abandoned castles in enormous caverns, complex mazes, huge and elaborate portal dungeons. Small buildings on the surface could have tunnels that lead down into underground jungles of glowing things.
Now the squid comes back into play. You get a special item from it that lets you make any dye glow. So we get glowing concrete and wool and stuff. But more importantly, glowing armor.
Deep in the caves, powerful monsters will attack and kill you if you aren't glowing like them. But if you kill one, you get powerful items in return. So you have dimly glowing armor. It keeps them away. But as a trade-off, it attracts other, less powerful things to you. Now these would be a mix of passive and aggressive mobs. But most would work like wolves or zombie pigmen.
The armor would glow more when underwater.
And more ores would be added. None better than diamond or netherite of course, but they'd have their own special bonuses. One could be better against deep sea monsters. Another could have low base damage but inflict high fire damage and the armor could make the wearer temporarily immune to lava, but being in nether lava destroys the armor quickly.