One feature I would find helpful is to change the price of any card under a set tcgmid price (50 cents? a dollar?) to the tcglow price. For most cards, this is a more accurate reflection of their values. Bulk commons tend to have a tcg median price of about .25, but no one values them at the tcgmid (for good reason). I have no idea if this is possible or not.

Maybe the ability to toggle to tcg for trades in general would be doable?

You can't do it easily trade by trade, but you can set the preferred price used for your account. Just visit your Settings page.