Given the premise that sufficient proof existed of hireling propagandist trolls, (let's say there was something like an auditable Wikileaks troll list such that it could be confirmed), I'd suggest:

 1.  The users in question should be banned from future activity, barring some future evidence that exonerates them.

 2. No deletions of troll accounts, comments, answers, or questions unless the posts are
    offensive  on some other grounds.  A known troll's postings would be
    valuable in of themselves, keeping them around would:
    
    * Show that SE doesn't hide problems.
    * Show users what troll posts look like, and how they may differ from ordinary user posts.
    * Provide meta-data, if any, on what a troll's employers are interested in.
    * Have value as humor.
    * May preserve some otherwise unobjectionable and useful answers.
 3. Keep their posts public mostly as before, with certain allowances:  
    
    * All votes from non-Trolls should remain as before.  
    * Votes from actual trolls should be printed alongside the legitimate votes, with some clear indication that those votes should be regarded as fraudulent.
    * All troll posts could be in a conspicuous troll-font, perhaps like one of these [Halloween fonts][1], perhaps with a conspicuous
    background color, and accompanied by some kind of troll-ish icon.
 4. For those who'd prefer to forget, or don't want any static, some
    kind of user option, perhaps in on a config page, to disable the
    display of any of the above, (votes, text, *etc.*).  For those users, SE would look the same as it does now, minus any known troll posts.

 5. The user page of a known troll should make it clear that the user
    was a known troll, (special fonts and icons would help), with as
    much general data as can be had, perhaps using special troll tags.
    
    An example of a troll tag would be if a troll was known to have
    worked for IRASP or whoever, there could be an IRASP tag, or whoever, which would link to a list of every other known troll with
    that employer.  Or a more general tag indicating, if known, the political power
    bloc that employer is allied with.

  [1]: http://www.fontspace.com/category/halloween