When you are building a table, you have the option to add a model field or a template field. Seems like offering child relationship and model look up options here would make them much more likely for declarive guys like me to use. model look up is not impossible, but you have to dig through the community to even know it exists. Child files are functional but not intuitive to set up. You could spoon feed the process to the user and make them much more accessible.
Related to this: UI only field type “model look up”.