The problem with "Large Endgame Maps just need more content".

What content is this going to be?

Is it going to be random content? If so, I don't see how this is a Solution, because players specifically want to target farm their chosen League Mechanics, so adding additional random content, which you don't have Atlas bonuses for, is not going to be anymore desirable.

The only way I see this working, is if your League Mechanic scales with the size of the map.

E.g. You're trying to farm Expedition, and larger maps contain 2 or 3 Expeditions, compared to just 1 Expedition for the smallest of Maps.

Maybe 3 categories of Maps:

Small = 1 x League Mechanics

Medium = 2 x League Mechanics

Large = 3x League Mechanics

The other obvious downside to bigger maps, with the new Atlas design, is that smaller maps are always going to be preferred to maximise progression speed. Or something simple like getting to a Unique map in the distance, if that's your goal then it's always preferrable to go through 3 small maps than 3 large ones.

I feel like the Atlas design, where you have little choice in the maps you complete compared to PoE 1, is at some point a deliberate attempt to make this less of a concern, where in PoE 1 you're fundamentally trying to farm the same map over and over. But PoE 2 hasn't even come close to solving this problem yet, and it's current design makes the Endgame much less enjoyable than in PoE 1.