it's not really possible considering that most retirement accounts are stock portfolios — it also doesn't matter too much on an individual level because an individual ban just gets pushed to sharing stock tips with extended family (already happens), family bans get pushed to friends, etc...

I really think the best and maybe only way to avoid this wealth building nonsense are much harsher term limits — public service should be severely limited to prevent people from being in decades long positions to abuse it. Term limits also prevent the incessant campaign fundraising to some extent, because say you're limited to 2 terms... there's not much point in personal fundraising on your last one