This is something I have thought about since the game first came out, I think it would be cool to have a tower invasion mode. Once there is enough guardians in the tower sirens go off to warn everyone to prepare for the coming battle. While this is happening all vendors except the vanguards will go to a safe zone. The vanguards split up and each one leads the guardians in a part of the tower. One group by the speaker, one by the main area, and one over in the hanger. When everyone is in place the fallen start to crawl over the walls and in to the city. If a side of the tower is overrun the group will retreat to the entrance of that side, if the middle is over run they will retreat to the hall of vanguards. If this happens the tower will send a distress signal to guardians to come help. If the back up does not come the guardians will be given heavy ammo. If the fallen get to close blast doors will shut keeping the fallen out until they decide to leave. This will leave the tower in need of repairs, guardians will walk around picking things up and placing them back and maybe a small cutscene of guardians picking up. If no points are lost in the battle the guardians will legendary drop with a small chance of an exotic if one point is lost it will be just a legendary, if two points are lost it is a roll for either two or three blue engrams, if three points are lost it will be just a blue engram, if all points are lost and the blast doors closed there will be no reward. If you are here thank you for reading all the way through  Feel free to change it up a little and spread ideas let me know if you thought it was a cool idea or not.