First of all, what happens if you charge a pack that has a separate channel for charging through the discharge wires?
AND, if it is not recommended, how will regen work without damaging anything?
You can charge through the discharge port - the problem is that the BMS won't cut off charging if a cell hits HVC, so you have to monitor your cell balance and terminal charge voltage. There's no problem doing regen through the discharge leads, as long as you don't start fully charged at the top of a big hill, and you limit the regen current to a safe level.