I made something like this to use for an RPG I never got around to finishing.
Through a series of clientCmds, you can custom prompt, with a title, message, and a limitless (well, limited by screen resolution, since I didn't put them in a scrollCtrl) amount of buttons for different choices, each with a different callback, and resizes the window and positions the buttons to look nice.
Never saw the need to make them into events (event gamemode are really stuffty IMO) but doing so wouldn't be hard.
The problem is that it requires a client-side download.