It might not be a 100% parallel but its close to what you mentioned and the precedent was already there for your Trump/Vance scenario. Ford pardoned Nixon for any and all crimes that might have been committed during his Presidency. Nixon maintained that he never committed any crimes. No specific crime was mentioned in the pardon and there was a timeframe element to it as Nixon's presidency had a definite beginning and end.I've never actually read the pardon for Nixon which happened over 50 years ago. Was it this open-ended?
Also Nixon was not impeached but threatened with it. IMHO, after Clinton was let off the hook , Nixon was owed an apology.
Presidential impeachments have been and will probably continue to be a toothless joke going forward.