This is definitely possible, I just tried it myself and it works, I was able to freeze / unfreeze other users using Skuid. (I added a Condition on my UserLogin model to exclude Logins for the running user, though, i.e. to prevent me from freezing myself).

The UserID column is not showing up because of “standard object weirdness” — the UserId Reference field here doesn’t support SOQL queries across it to the User object, so Skuid doesn’t have a “Name” to display for the User (since Skuid tries to always show Names instead of Ids when displaying Reference fields). To get the raw UserId field value to show up, Add a Template field to the table, with the contents being {{{UserId}}} (with three braces on either side).

Thanks, Zach.  I appreciate the explanation and the excellent addition of the running user exclusion.  This will be soooo nice to have during our next deployment.