Is possible to order the line in a one2many without to modify the original class order?
Finally, I found a way to manage this, downloading this module:
Then, I overrided the one2many whose order I want to alter, in my case the field was child_ids, and I wanted it to be ordered by email:
'child_ids' : one2many_sorted.one2many_sorted(
Note that the only difference between this field and the one2many is the param order (you can use a couple new more though, search and set).
I also imported the library at the top of the file:
Now, I'm seeing the tree and kanban of res.partner ordered by name, but this one2many is ordered by email. Great!