Eg:

=> [
     "agg-hello" => [
       "BASIC" => [
         "id" => "agg-hello",
         "label" => "hello",
         "description" => "hello",
         "meta" => 1,
         "class" => "AggregateMessageGroup",
         "namespace" => 1198,
       ],
       "GROUPS" => [
         "page-T*,
       ],
     ],
   ]

This would mean that the subgroups of the aggregate group would be dynamic, evaluated during runtime. This means that the aggregate group cache need not be purged when new pages are marked for translation or removed from translation. It also simplifies the job of a translation admin who doesn't need to go add every subpage to the aggregate group separately.

This is already possible for aggregate groups configured through yaml, but not for those configured through the wiki. This would both reduce key size and make their management easier.