Database design: Storing app defaults

Hi list.

If you have a table like this:

table1
- id
- field1
- field2
- field3

table2
- id
- table1_id
- field1
- field2
- field3

table1 & table2 are setup as 1-to-many.

If I want to start providing user-customizable defaults to the
database (ie, we don't want apps to update database schema), is it ok
database design to add a table2 record, with a NULL table1_id field?

In other words, if table1 has no matching table2 record, then the app
will use the table2 record with a NULL table1_id field to get
defaults.

This looks messy however. Is there a better way to do it?

A few other ways I can think of:

1) Have an extra table1 record (with string fields containing
'DEFAULT'), against which the extra table2 record is linked.

2) Have a new table, just for defaults, like this:

table2_defaults
- field1
- field2
- field3

Which is the cleanest way? Is there another method I should use instead?

David.