You improved on the textures and all the problems Heretical-Cyborg had initially. I still think it's a little cramped for playing Marathon though...
My recommendation for copying a Doom-Engine map would be to copy E1M1 from the original doom. Would be a great for Marathon. (Could you copy the first seven Doom maps and put them in mini-scenario, please?)
I also have a problem wih RyokoTK's remark about "how boring Heretic is". Lies!
Heretical Cyborg is VikingBoyBilly's first complete single player map. It is also customized for co-operative play. It is modeled after the first map of Heretic, E1M1 "The Docks," and is an attempt at remaking a Doom-engine map into the Marathon Infinity Engine.
It started off as an entry for Kill Them All: Volume IV, but the polygon count went up too high. Instead of letting it go to waste, here is this completed standalone map for you to play.