Publicly announcing trades many months ahead should be enough, without having to get too radical about it.

It pretty much prevents benefiting from "subtle insider" trading via being lobbied by corporate officials or getting any friendly hints from them. The problem with "follow Nancy's trades" idea is that by the time the trade is known, the price has already corrected. The first one to complete the trade is often the only one to collect a significant benefit, the followers get scraps.

And it indirectly disincentivizes owning individual stock because prearranged trade of one stock carries a risk of being screwed by market manipulators, while prearranged trade of a broad index fund is not a problem.