When this question was asked, nothing in the system prevented users with recent suspensions from standing for election. When those candidates stood, there was invariably drama. Sometimes the drama overwhelmed the election, leaving everybody feeling a little dirty at a time when we should be happy to be electing more caretakers for a site. Even when a candidate with a recent suspension is elected anyway and does fine as a moderator, the drama lingers.
That's why users who have been suspended anywhere on the network within the last year are now barred from standing for election. The check is manual, not automatic, so that if there were extenuating circumstances, the Community team can still decide to let a nomination proceed. But in the cases you're worried about -- those suspensions that you would want to be disclosed -- those users just can't be candidates now in the first place.
A year is long enough. We don't need to shame users for years and years because of some long-since-corrected screwup. We probably all have things we've done in the distant past that we're not proud of, things we'd like to make disappear but the Internet is forever. Ancient suspensions don't need to be trotted out in every election.
If somebody with a bad record is still causing problems somewhere, you can rely on somebody bringing it up, and then voters will know.