We would always be happy to hear of suggested new features. For every program, there are already lists of features that we are planning to add. You can see the current list of plans from the Gnuastro project web page at https://savannah.gnu.org/projects/gnuastro/ and following “Tasks”→“Browse” on the horizontal menu at the top of the page immediately under the title, see Gnuastro project webpage. If you want to request a feature to an existing program, click on the “Display Criteria” above the list and under “Category”, choose that particular program. Under “Category” you can also see the existing suggestions for new programs or other cases like installation, documentation or libraries. Also, be sure to set the “Open/Closed” value to “Any”.
If the feature you want to suggest is not already listed in the task manager, then follow the steps that are fully described in Report a bug. Please have in mind that the developers are all busy with their own astronomical research, and implementing existing “task”s to add or resolve bugs. Gnuastro is a volunteer effort and none of the developers are paid for their hard work. So, although we will try our best, please do not expect for your suggested feature to be immediately included (for the next release of Gnuastro).
The best person to apply the exciting new feature you have in mind is you, since you have the motivation and need. In fact, Gnuastro is designed for making it as easy as possible for you to hack into it (add new features, change existing ones and so on), see Gnuastro manifesto: Science and its tools. Please have a look at the chapter devoted to developing (Developing) and start applying your desired feature. Once you have added it, you can use it for your own work and if you feel you want others to benefit from your work, you can request for it to become part of Gnuastro. You can then join the developers and start maintaining your own part of Gnuastro. If you choose to take this path of action please contact us beforehand (Report a bug) so we can avoid possible duplicate activities and get interested people in contact.
Gnuastro is a collection of low level programs: As described in Program design philosophy, a founding principle of Gnuastro is that each library or program should be basic and low-level. High level jobs should be done by running the separate programs or using separate functions in succession through a shell script or calling the libraries by higher level functions, see the examples in Tutorials. So when making the suggestions please consider how your desired job can best be broken into separate steps and modularized.