First and foremost, Stanza was designed for myself, to solve the problems that I repeatedly face in my own programming.
I mostly write software that is end-user-facing and interactive, with requirements that aren't known at the beginning of the project. Software that my mother would use, is how I typically describe them. e.g. Word processors, games, calendars, photo albums, spreadsheets, maps, movie players, etc.
And what I saw repeatedly, for all of my projects, was that progress comes a lot faster in the beginning than near the end. Eventually, I pinpointed the problem to one of software architecture. It is easy to see the required architecture for the start of a project, and making progress is easy. As you pile on demands and features, you realize that the architecture that you started off with is wrong, and progress slows. This is especially true if the requirements of your program are not known in advance. I expect people that mostly program well-known and stable algorithms don't have as much difficulty with this. E.g. numerical linear algebra, schedulers, image filters, etc. That is not what I write.
Once you realize that your architecture is wrong, you have two choices. You can either plow ahead with a sub-optimal architecture, and take a small but continual productivity hit. Or you can try to refactor and correct the architecture, and take a large one-time productivity hit. Neither approach is satisfactory. Small continual productivity hits eventually add up to the point that forward progress is seriously impeded. Refactoring also costs a lot of time, and eventually the cost of refactoring becomes too great to be worth it, and you're stuck with the last good enough architecture that existed.
So Stanza was designed to make it possible for me to :
1. Experiment easily without specifying upfront the class inheritance tree in the program.
2. Delay committing to a specific architecture for as long as possible.
3. Refactor the underlying architecture of a program through small local changes.
And for the programs that I write, I sincerely believe that I succeeded. I've been programming exclusively in Stanza for about three years now, and I haven't yet ran into the dreaded "refactor-or-abort" situations that arise often in Java/C++ programming. Radical changes to the underlying architecture of a program are possible by applying a series of small staged local changes. And the optional type system allows me to get a lot of features working without having to commit to an architecture, so that when I finally sit down to properly design the architecture it is much more likely to be correct.
So my ultimate goal with Stanza is to help you achieve a linear rate of progress across the project timeline. You should feel as productive near the end of the project as you did in the beginning of the project.