add expressions at the database field level

I am working with http://drupal.org/project/timefield and I want to get a field, sort, argument, and filter for a timefield's duration. This is simply a matter of adding an expression 'value2 - value' to the query, so it seems rather wasteful that it requires a whole new handler for each of sort, filter, and argument.

So I'm wondering: what if this were built into Views?

One way might be to provide a generic handler for each type, and have the hook_views_data() definition specify an expression like this:

 'mytable' => array(
  'my_expression_field' => array(
    'sort' => array(
      'handler' => 'views_handler_sort_expression',
      'expression' => 'value2 - value',

However, if instead of that we do this at the base class level for each type would mean that a definition in hook_views_data() could use any handler, eg views_handler_filter_in_operator. So:

 'mytable' => array(
  'my_expression_field' => array(
    'sort' => array(
      'handler' => 'views_handler_filter_in_operator',
      'expression' => 'value2 - value', // This is handled in the views_handler_filter class.

However, that would be a lot of reworking of the query() methods, or having the alias to the expression in $this->real_field to fool all the existing code which would be a bit of a DX WTF.

So not sure which approach is best. Maybe a) for now and save b) for Views 4?