This one depends on HD becoming an option for the Rev. I know this may not happen, so if you're going to reply indicating that fallacy in my premise, don't bother.
We already know that the Rev will be a few times as powerful as the GCN. We also know that it supports the GCN's API, and can assume that it supports it's instruction set. Assuming this, it should be possible, with little work to make current GCN games work at HD resolutions. In fact they could be sold as downloadable executeables. So here's the idea. Nintendo wants to squeeze a few more yen out of Twilight Princess. So you pop your copy of TP into the Rev, and instead of booting directly to the game, it checks to see if there is an HD update for the game. It checks against it's database that it periodically updates online. If there is one, it offers for sell a copy to you for $5. What you end up getting is a recompiled executeable that supports widescreen and HD resolutions along with updated 2d textures (like menu items and such) and updates for textures that are used very commonly in the game. This should take 1 programmer and 1 artist about 1 month to produce, for maybe $15000 in production costs (salaries + other resources). They recoup their losses after 3000 sales.
Additionally they could release these on store shelves as "Revolution Enhanced' versions.
Other things that could be done would be enhanced controls for some games like monkeyball and RE4.