Disabling Gainsight users from deleting or adding customer accounts

We are importing customers from Salesforce and want to prevent the CSM from being able to delete and add their own customers.  Currently this is not part of the product.
should be restricted to GS admin or other permission level - not to all CSMs
Would restricting access to the Customers Tab work?  We could remove access to that page for all CSMs, and replace it with a dashboard that lists out all the customers + Scorecard mass-edit, etc.
And can we also use the new Summary Widgets to re-create the totals that you see across the top of the Customers tab on the new Customers dashboard? (If any CSMs need to edit stage, comments, or Tags that would need to be done from the C360, correct?)
Yes, all four widgets can be recreated using the new widget report type, just have to apply the same filters on all of them for the numbers to connect to the customer list. You'd have more flexibility actually, as you could choose to replace [i]SUM of Users with [i]AVG of Current Health Score, for example.

Yes, those edits would have to be done one customer at a time, from the respective 360 views. And we also lose the mass-tagging capability (having the Scorecard mass-edit available to you compensates significantly though).
One more thing to note: Inline filters on a dashboard report won't search across all customers -- they are client-side unlike server-side on the Customers tab. Don't think this is a bottleneck though, since you can still get this filtering by (1) clicking on the filter icon on the top-right instead; or (2) using dashboard filters that apply to all reports.
@Manu's original post

I like the idea of a mass edit, however, I don't think restricting the customer view is the right approach.  I think having the holistic view can be helpful with customer searches and for CSM coverage.

Just to clarify, here's the Customers tab view next to its replica I created as a dashboard (with five reports):

I like this , but as with other widgets add some color or border to make it more eye appealing.
Absolutely! We do plan on making these widgets more visually appealing, and are also exploring conditional formatting to give you control over what colors show up. Not sure about the ETA yet.
is it possible to also allow for clicking on the widget to pull up the data behind it like you do for a container type report where you can configure what columns and such pull up when the widget is clicked?  
What's the progress on this?

And restricting access to the customers tab is a terrible idea. That's where CSMs can access a list of their customers. I recommend removing the Trashcan  Icon (delete) from the customers tab and also disable the ability to "Add Account" from the SFDC Account.