There will be no penalties until the Republicans can take the Senate. The Dems can block, stall, and destroy evidence with impunity without fear of oversight. Once there is a real threat of impeachment then we will see if they have the guts to do anything.
The House could hold them in civil contempt and hold them in one of the pocket offices in the House Office building since t h st no longer have a jail sell. Remove all the furniture except a bed with a prison mattress, table, chair shelf, small TV and what ever minimum requirements there are for a jail cell. In an outer office they could put some exercise equipment. They theoretically could hold them until January and as soon as the next House session hold them for another 2 years. Since this would be an action by the House they could argue that their action is not subject to judicial review under separation of powers and refuse to release him until all appeals are completed. If Holder sends the FUN to spring him, block them with their own bodies.