Programmatically add existing entities to a solution in CRM Online

CRM Online

Folks,

We're migrating some on-premise organizations to CRM Online.  Part of the migration work is to migrate custom fields that our end users create with their own non-managed solution.

I can extract the custom fields from the on-premise customizations.xml filed (as you know, this file is within the non-managed solution zip file) and determine which entities have custom fields.

Now I can display this entities list and our migration team can manually add the entities and dependencies to the target solution, but it would be nice if I can programmatically do this for them.

Is there a way to do this using the IOrganizationService?  Note that I don't want to create entities, I just want to add existing entities to a specific solution.

Thanks