The one good thing from an impeachment is that Trump would never be able to hold office again.
Here's the problem, and you're trying to have it both ways on this.
If you believe in rule of law, but don't believe you can convict in a court of law, so you'll use a political court to achieve your goals instead.
You don't support the rule of law, you support rule by fiat.
If you believe in the people being able to make their own choices
through the use of democratic processes. Then you cannot support using Impeachment as a mechanism to prevent someone from running for office again. That should be a decision made by the voters, not 218 members of the House and 67 members of the Senate.
If you support impeaching Trump simply because you're afraid he could run for office again
and win, then you don't support Democracy either.
If you don't think Trump is going to be able to win a Presidential race again in the future, then why are you impeaching him after he left office?