Hmmm... ok, so I still like the idea of lab 1 being down there, because of the background Evil picked for that area. So, basically have another good old abandoned lab (we don't have a lab 1 yet, and it might just make since that they get to the winter alter with their first lab), this one surrounding the original alter to the winter god. And that is an interesting idea of it being only accessible after summer is returned.
Hmmm... so I'm all for getting this done quicker, but if we do both the balanced and the tropical ending, it seems we might just have to have a thawed version of the level, which would not be quicker. If people want to do it, that's fine, but I'm starting to wander if all we really should to, at least for now, is either power up the summer alter or power down the winter alter. I'm leaning towards the later. Once that is done, to a quick end scene, and we're good. Later, after we are done, if we REALLY wanted to we could make the third ending and all the extra work that entails.