Hexen Death kings as an episode?

I was wondering if Hexen's Death Kings of the Dark Citadel could be setup as a selectable episode the same was you can add a wad as an episode in Doom/II in g/zdoom?

Yes, but you'll probably want to copy the levels to a PWAD instead first, and then make a new MAPINFO. The reason for not using the hexdd IWAD directly is that the deathmatch levels in Death Kings use map slots corresponding to normal levels in Hexen.

Look here, as that's the only place in the Doom wiki where Hexen levels are actually mentioned by their slots.