Hello Julien,
Custom Inputs would be hard to do in a non-hackish way. Low code tools are quite complex; when adding a custom input, we would need to deal not only with the input itself but how the application schema (meta data about the application) deals with it and how application updates work. Because REI3 allows transfering applications between instances, of which only some might have these custom inputs, it would be quite the headache. If you do not care about this, it would be simpler but then you loose all options for upgrades in the future.
You could more easily replace existing inputs with custom ones by directly editing the frontend source code. As long as just the input changes but the data stays the same, at least the application schema and backend do not need to be updated as well. Your inputs would then be custom only in the instances you directly supplied with your updated frontend code.
May I ask what kind of inputs you are looking for? We might not be able to quickly address all requests, but we are interested in what people want, so that we can plan ahead and add these features, when it makes sense.
