I was looking over the Quest GamebookCore to answer somebody else's question, and an idea popped into my head.

Would it be possible to combine gamebook and text adventure, to make a hybrid format? Including all the types and functions from both core sets. All the gamebook page types would inherit a new type gamebookpage to make them identifiable.

Then you'd give the player object the changedparent script from the Text Adventure mode, but change a couple of functions like so:

  <function name="OnEnterRoom" parameters="oldRoom">
    <![CDATA[
    game.displayroomdescriptiononstart = false
    if (IsDefined("oldRoom")) {
      if (oldRoom <> null) {
        if (game.clearscreenonroomenter) {
          ClearScreen
          if (HasString (game, "currentexitmessage")) {
            msg(game.currentexitmessage)
            game.currentexitmessage = null
          }
        }
        if (HasScript(oldRoom, "onexit")) {
          do (oldRoom, "onexit")
        }
      }
    }
   
    on ready {
      if (DoesInherit (game.pov.parent, "gamebookpage")) {
        game.gamebookdisplay = true
        DoPage (game.pov.parent)
      }
      else {
        game.gamebookdisplay = false
        if ((not GetBoolean(game.pov.parent, "visited")) and HasScript(game.pov.parent, "beforefirstenter")) {
          do (game.pov.parent, "beforefirstenter")
        }
 
        on ready {
          if (HasScript(game.pov.parent, "beforeenter")) {
            do (game.pov.parent, "beforeenter")
          }

          on ready {
            if (game.gridmap) {
              Grid_CalculateMapCoordinates (game.pov.parent, game.pov)
              Grid_DrawPlayerInRoom (game.pov.parent)
            }

            if (IsDefined("oldRoom")) {
              if (oldRoom <> null and game.changeroom_newline and not game.command_newline) {
                msg ("")
              }     
            }

            JS.updateLocation(CapFirst(GetDisplayName(game.pov.parent)))
            roomFrameExists = false
            if (HasString(game.pov.parent, "picture")) {
              if (LengthOf(game.pov.parent.picture) > 0) {
                roomFrameExists = true
                SetFramePicture(game.pov.parent.picture)
              }
            }
            if (game.clearframe and not roomFrameExists) {
              ClearFramePicture
            }
            if (game.showdescriptiononenter) {
              ShowRoomDescription
            }

            if (HasScript( game, "roomenter")) {
              do (game, "roomenter")
            }
            on ready {
              if ((not GetBoolean(game.pov.parent, "visited")) and HasScript(game.pov.parent, "firstenter")) {
                do (game.pov.parent, "firstenter")
              }
              on ready {
                if (HasScript(game.pov.parent, "enter")) {
                  do (game.pov.parent, "enter")
                }
              }
              set (game.pov.parent, "visited", true)
            }
          }
        } 
      }
    }
    ]]>
  </function>

  <function name="InitInterface">
    <![CDATA[
      if (GetBoolean (game, "gamebookdisplay")) {
        JS.uiHide ("#txtCommandDiv,#location,#gamePanel,#gridPanel")
        JS.panesVisible (false)
      }
      else {
        // contents of current TA InitInterface here
      }
    ]]>
  </function>

  <function name="HandleCommand" parameters="command, metadata">
    <![CDATA[
    handled = false
    // Moved to the beginning so you can do transcript comments while a menu is visible
    if (StartsWith (command, "*")) {
      // Modified by KV to bypass turn scripts and turn counts, and to print "Noted."
      game.suppressturnscripts = true
      msg ("")
      msg (SafeXML (command))
      msg("Noted.")
      // Added for Quest 5.8    - KV
      FinishTurn
      handled = true
    }
    if (game.menucallback <> null) {
      if (HandleMenuTextResponse(command)) {
        handled = true
      }
      else {
        if (game.menuallowcancel and not handled) {
          ClearMenu
        }
        else {
          handled = true
        }
      }
    }
    if (HasAttribute(game.pov.parent, "options") and not handled) {
      if (DictionaryContains(game.pov.parent.options, command)) {
        if (not GetBoolean (game, "clearlastpage")) {
          optiontext = StringDictionaryItem(player.parent.options, command)
          msg ("<b>" + optiontext + "</b>")
          msg ("")
        }
        JS.disableAllCommandLinks()
        game.pov.parent = GetObject(command)
        handled = true
      }
    }
    if (not handled) {
      StartTurnOutputSection
      shownlink = false
      if (game.echocommand) {
        if (metadata <> null and game.enablehyperlinks and game.echohyperlinks) {
          foreach (key, metadata) {
            if (EndsWith(command, key)) {
              objectname = StringDictionaryItem(metadata, key)
              object = GetObject(objectname)
              if (object <> null) {
                msg ("")
                msg ("&gt; " + Left(command, LengthOf(command) - LengthOf(key)) + "{object:" + object.name + "}" )
                shownlink = true
              }
            }
          }
        }
        if (not shownlink) {
          msg ("")
          OutputTextRaw ("&gt; " + SafeXML(command))
        }
      }
      if (game.command_newline) {
        msg ("")
      }
      game.pov.commandmetadata = metadata
      if (game.multiplecommands){
        commands = Split(command, ".")
        if (ListCount(commands) = 1) {
          game.pov.commandqueue = null
          HandleSingleCommand (Trim(command))
        }
        else {
          game.pov.commandqueue = commands
          HandleNextCommandQueueItem
        }
      }
      else {
        game.pov.commandqueue = null
        HandleSingleCommand (Trim(command))
      }
    }
    ]]>
  </function>

You'd also want to make a script game.changedgamebookdisplay which just calls InitInterface().

Not sure if there's other elements that would need showing/hiding. But I think I've seen a few people who would have liked the ability to mix and match gamebook and text adventure sections in the same game :p

This is just off the top of my head, but it's been bouncing around in my mind for a while. Would this be a useful library? Overrides a couple of core functions, and allows you to include gamebook sections within a text adventure.

Is it possible? Yes.

Is it possible using your code example? To be humble, i only skimmed it.

The thing is: gamebook mode is infact just the inferior cousin of TA so far (speaking of first hand experience with it's limitations; there are literally only three kinds of objects game, player and page) and everything you can do in CYOA can be done with parser-based games, probably even better.

There is a library to hide the parser, inventory and the rest of the TA UI, but i think you already know that. So you only have to en-/disable it in time.

Also, i think there has been mixed CYOA/TA games on this site already, but i can't remember a game title right now.