This isn't exactly an idea for a (G)ZDoom project per say, rather a kind of enhanced feature for map interaction. I'm not a programmer so I doubt this is feasible since it would probably require major engine changes, but what I imagined was like this:
Multiswitches, which are a kind of specialized, in-game GUI-based switch with multiple switchable areas, can be toggled and execute on/off scripts, and are just generally more versatile/immersively interactive than normal switches.
You create an image like this:
switchblank.png
It is the Multiswitch Base. It includes at least one blank area (although it doesnt actually matter what that blank area is, its just blank here for demonstration purposes.) You then feed this into an external Multiswitch Editor. The editor allows you to drag boxes around areas switches will be placed. When a switch-spot has been created, you can click to define certain attributes of that switch, such as how many states it has (ie you can have a four-way state switch like that one in Doom's Alpha), how the state behaves (ie whether or not it can only be switched on, if it switches on then goes off by itself and can thus be reactivated, or whether its toggleable and can be turned on and off.), as well as what switch graphic it uses. Because it would be impractical to make new switch pictures for every combination of switches that are on and off, switch graphics are created with on/off states separately:
switchoff.png
switchon.png
Once you've defined the multiswitch in the editor, you press "generate" to make it generate the parameters of the multiswitch. Now, (in slade for example), you can paste this multiswitch code into your wad or pk3, assign it an ID and a switch texture, add the multiswitch graphics, then load your map in an editor.
Now, you can add the switch texture to the map. When you right click it, the Edit Linedef box has a tab specifically for controlling the multiswitch's properties, such as assigning scripts or line actions to each switch based off its behavior. In the example switch I made, assuming each switch is toggleable, different scripts can be assigned to execute when the switch goes to its on or off state. For example, suppose one switch controlled a security door somewhere in the map, toggling the switch "on" would probably open the door, whereas toggling it "off" would execute a script to close the door again. In the different behaviors, it works similar. The on-stay switch stays on when you press it, meaning it executes its script once and then becomes uninteractable. The on-repeat switch can be pressed over and over again, each time executing the same script (so for example you could have a switch which raises a platform by a certain increment each time its pressed, whereas another switch in the multiswitch lowers it by the same increment.
The most special part of this feature is how its interacted with in-game. When a player uses the switch, it opens a GUI menu in-game, dimming the game view. You can exit out of it by either walking away from the switch or pressing use again. To interactive with the switch, you use the mouse to click around and use the various switches on the GUI.
While this obviously wouldn't be something with universal use, it would be a very good way of creating puzzles or implementing interactable elements, especially in more atmosphere-focused maps. Though I will admit, I doubt its very feasible, its still a very interesting idea I think.
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