This will make many guardians happy. Add a difficulty setting. Add rewards for progression in the waves of battle. Example: after reaching wave 20 (it would be difficult) awarded blue engrams. And reaching wave 30 or 40, chance of getting purple. And after reaching 50-70 an even HIGHER chance of purple. And after reaching 100 (a highly difficult feat that will require huge amounts of communication) Exotic engram. You can even make it to where after every ten waves, a part of your hud disappears.