Abstract model with dynamic fields

Question

I am wondering since ages how to achieve the following:

I have an abstract class wrapping several attributes shared by multiple models. But not every model needs every attribute in exactly the same way.

Here is an example: MyModelA and MyModelB both have two fields: value_1 and value_2. But while MyModelA needs them to be required/not nullable, they can be nullable for MyModelB.

class MyAbstractModel(models.Model):
    value_1 = models.IntegerField()
    value_2 = models.IntegerField()

    class Meta:
         abstract = True

What I tried:

1. Not deriving MyAbstractModel from models.Model but from object like a regular mixin

2. Setting a class attribute which is overwritten in the child classes to determine the nullable-state. It always takes the definition from MyAbstractModel.

3. Using a class attribute but not set it in the MyAbstractModel. Then the makemigrations command fails because of the undefined variable.

4. Cry

Being DRY is such an important paradigm in django, I really wonder that there is nothing on this topic in the internet.

Thanks in advance!