I've been pondering this, and I've come up with an idea that will allow us to have a rather large mountain with a relatively small base of support. However, it will require placing some of it on another Map. (No, it's not what you think. See attachment.)
Also, I kind of like the visual image of a massive pillar of stone, snow and fire piercing the sky.
EDIT: I also have a reasonably excellent MIDI to use for the mountain ascent. It requires, however, that there be a significant level of snowfall on most of the mountain's screens. It's called Winter Wind, and it's an all-piano piece - but it's by Chopin so it doesn't matter.