Here's my usecase:

I need my client to be able to set up configuration connecting Google CSE IDs with pages, for example

CSE ID 1: abc123xyz
PAGE 1: global-search
LANG 1: en

CSE ID 2: xyz123abc
PAGE 2: global-search
LANG 2: fr

CSE ID 3: xyz123456
PAGE 3: product-search
LANG 3: en

etc.

Would it be possible/desirable to implement this in the config_builder? I'm thinking of something like the following:

fieldset (machine name my_fieldset):

[x] repeatable
[x] save child data in fieldset variable (always on when repeatable is on)

fieldset contains:

- CSD ID
- PAGE
- LANG

The variable can then be retrieved as follows:

variable_get('my_fieldset', array()) = array(
  array(
    'cse_id' => 'abc123xyz',
    'page' => 'global_search',
    'lang' => 'fr',
  ),
  ...
);