While I do believe this is how it could happen, there is a slight problem in that theory. The only way we know of to distort space is by placing and condensing a central mass in an area of space to connect the area around it. By doing that though all matter in it the compressed area is crushed to the point of dust (maybe even less) and to traverse said singularity of mass, you would have to be moving at a speed faster than light so as not to get sucked in (which is where allomancy comes in.) I would best describe as a spread blanket (only it's a four-dimensional blanket). If you drop a bowling ball in the middle, it will warp the matter around it causing the traversal in between to cost less time. If you were to roll a toy car over the horizon of the singularity condensing this space, you would have to either go around, or roll it fast enough to fly over the hole to get to the other side, effectively forcing the need for allomancy to compress to time and, to an extant, energy to do so.
If you could answer, I have a few questions for you in terms of the allomancy. How big of a bubble could you create if you were to use duralumin with cadmium? By any chance is there a metal that allows you to link your powers with other allomancers to make traversal possible? And another thing, how far into the timeline would this trilogy be, considering they might just have the technology we lack to warp without those risks? Au revoir! ☺☺☺