We have several clients who use this pattern.
These are a couple possibilities/methods and of course mix and match is possible.
First off: I do not recommend you push the sales to the CRM until after they pass the verification officer. Since they may not really be a sale.
Use a dispo url script to move sales to a specific list. This list will be in a verification campaign. You can also modify the dispo script to change the lead to "not called" so it can automatically be called when a verifier is available on that new (verification) campaign.
Have special dispos in that campaign for Passed vs Failed and a new dispo url to push the sales back to the original list and even create a "callback" for the original agent (that's a little complex, of course, so you could just have the verifier do this directly when terminating the call by setting as a special status that happens to be a callback status, but you'd need to work out how to assign it to the appropriate agent).
We also have the QC (quality control) module which is not part of Vicidial (It's an Add-On) but is available to the general public. The sponsor of it recently asked for it to be published. Upon request we will provide installation instructions or install it for you for $100 (beta users). This fee includes upgrading it to your version of Vicidial (since it is not part of Vicidial, it is "version dependent").
The QC module involves setting QC statuses and then an admin interface allowing an agent (with QC privileges) to log in and view/edit/call each record marked as a status that is set for QC (such as SALE). The result of the QC can be pass (QCPASS is then a real sale, and SALE is not, so QCPASS would be pushed to vTiger ...) cancel (QCCANC means this is no longer viable, no callback just canceled) or QCFAIL which will automatically send the lead back to the originating agent as a callback record (immediately showing in the callbacks for that agent).
Outside Vicidial, you could also set scripts to detect the status of the vTiger (or SugarCRM) lead and "take action" based on this status. Such as sending the lead to a Verification list/Campaign in Vicidial, and when the client answers, the verification script can pop up automatically or the vTiger record, so the verifier can validate the record.
Any of these can of course be mixed and matched based on your operational model.
Beware the limitations of vTiger 5.1 (too many leads will cause it to bog down ...) and later versions are not yet integrated with Vicidial. Sugar does not have the limitation issue, but is also not integrated with Vicidial. I will say, however, that Sugar's code is written better ... but it is missing a key feature: Group Security. So your operational model must be used to determine the best fit.
Happy Hunting