I really like the whole levels system that was introduced with the tundra and would like to see it expanded to the other biomes.

Since eggs will no longer be available, the rewards for hgher levels will need to be changed. A good substitute might be an increased chance of finding the biome specific buildings and/or premium items.

I would also like to change how the portal energy cells are constructed so they don't require having a Lightning Strike roc or spending a fortune on charged sticks. (Storywise, perhaps the engineers discovered a more efficient type of energy cell when they studied the system in order to utilize it in the other biomes.)

Seconded! I've been loving travelling in the different levels of the tundra as well. It allows you to explore more without having to have the energy or Located Islands left to go to.

And if you're travelling with a high enough level pet you can sometimes find the 1.5k needed per level to make up for the cost of the charged stick. Or possibly find a portal energy cell on the map from the building.

I like this... Could be potential to earn more experience from explore by fighting harder monsters.