and how can I make it easier for them.

I am wary of this. It is very hard to predict what someone else in the future might want to do. I would only go so far as to ensure nothing I am doing will unnecessarily block a refactor later on but I would avoid trying to add or abstract things in ways that make the current code harder to read because you think it might be easier for someone to add to in the future.

I have needed, far too many times, to strip out some unused abstraction to do something that abstraction was never intended to allow because someone was trying to save me time and predict what might happen to the code in the future and got it completely wrong. It is far easier to add an abstraction to simple code later on when it actually helps then to try and figure out what the abstraction is and remove it when it is found to be wrong.