Those are some great ideas! You can also reward players for actually heading straight towards the exit, like refilling their health or adding an ally if they go to the end in 10 seconds for example, while also having the things you just mentioned. It would give players more ways to play the game, and adds a lot more replayability!
Also, not adding something that you already made but not putting it in the finished product because it breaks the game is a hard thing to do, good on you for making that decision!