Hi Bentraje, thanks for reaching out us.
With regard to your question, although hacks might be put in place to achieve the desired behavior - like using the logic behind a generator to perform a deformation -, it should be remarked that the suggested workflow contrasts with the logic behind Cinema modifiers.
The BaseObject::ModifyObject()
is indeed called by the scene execution pipeline, which is responsible for geometry handling and creation, only when the modifier has a parent object whilst it remains uncalled in all the other cases.
Cheers, Riccardo