While not quite as impressive as Ultima VII's debug menu, Pagan does have one of its own. However, you cannot access it via the command line; instead, you must hex-edit a game file to enable it. Use a hex editor to open AVATAR.DAT (located in the GAMEDAT directory) and change the values at offsets 2A and 2B to 01. Now start the game up and you should be able to utilize the key commands, as well as access the cheat menu by single-clicking on the Avatar.
I already showed off a few of its functions in the playthrough (namely Hackmover and being able to cast any spell, heedless of reagents or foci), but there are a few other features one can enable as well. The TCRF page has a comprehensive list.
I also tried to show off the memory/flag editor that comes up when you press F9, but unfortunately it doesn't seem to work very well under DOSBox (or in general, for that matter). As this page highlights, though, you can use it to enable some otherwise unused functions, including water-walking and lava-walking.
This page also shows off some other curious leftovers and extra items in the game.
Ultima VIII also has a cheat room of sorts, though it's also not as impressive as those of its predecessors. You get there from the Lower Catacombs, an entirely optional area accessible from the Upper Catacombs.
To get to the Lower Catacombs, head east from the Birthplace of Moriens sign in the Upper Catacombs, then head south, going past the ledge with the chest on it and a broken staircase to a gate. It will close as you approach; just go back and approach it again and it should open. Follow that path to the end to find a door labeled "To Lower Catacombs." Use the Key of the Scion to open it and enter.
This room contains almost every magical weapon in the game, as well as tons of explosives and scrolls and every type of shield and helmet. Walk to the south corner of the room to be teleported out.
For some more content that was cut from the game, check out this page on the Ultima Wiki.
And as ever, I also highly recommend IT-HE Software's anti-walkthrough of the game, which contains many sequence breaking tricks and other humorous tomfoolery.
