I've never heard of this group of "former special operations forces and intelligence community members," but they do sound like they know what they're talking about.
As we discussed here recently I think it's the obvious thing to do, and so obvious that in any other case it would have been done the same afternoon. Whatever you think about whether or not charges should be filed, there's simply no reason this shouldn't have been done at the first sign of clear evidence of document mishandling, even pending the investigation. You don't wait until someone is convicted to pull their clearance: they don't have a right to it, so there's no due process concern about life or liberty being taken from them, and you can always restore it later if they are vindicated. It's what we'd do with absolutely anyone else.
I know: she's above the law. She's above the rules. And that's why she needs to be President.