Revert persons to "non sync'ed record" when deleted in MS Dynamics or Salesforce

Currently, when a lead or contact is deleted in MS Dynamics or in Salesforce.com, the SFDC/Dynamics type fields and ID's  keep their values, and the person is still seen by Marketo as sync'ed. This means, amongst other things, that merging it in Marketo is simply impossible.

This is really painful because, in this situation, the only way out is to delete the lead (or May be ask support, but we are not going to log a support ticket everyday, are we?), but then we are losing all the activity log.

So this idea is that, when a lead or contact is deleted in the CRM, it should be possible to reverse the Marketo perso to a non sync'ed one. This would apply to the CRM Type field, to the ID field, but also to all the account information, if any.

-Greg