You just distracted yourself from your goal. Don't compound the error by chasing tomorrow. Find that simplest 20 and do it. Studies show that developers are not really that good at predicting what will be needed. It's better to wait for a real need, and provide for it then.
Smalltalk code is extremely easy to modify.
We do not have to design or build for the future. On the contrary , when I'm immersed in a new object, I may see how to do something that will later be more difficult because I won't be up to speed. If the object is so complex that it will be hard to modify later, it is just too complex. Simplify it so that adding new capabilities will be easy, but don't make it even more complex by adding them now. Your mission is to make the fastest progress against what the problem really is, not against what the problem might be or might become.