You know what I'd like to see? The armor from the very beginning of Destiny 1. Remember the armor your ghost literally made for you after your first resurrection? Basically that. Common rarity and everything, exactly the same stat-wise as the damaged armor from Destiny 2's campaign.
In addition, the following things should also return:
* Khvostov (both Common and Exotic variants)
* The original white ghost shell from Destiny 1.
* The first ship. Completely unchanged from its original appearance.
* The first sparrow, exactly the same.
* An undamaged variant of the Traveller's Chosen sidearm from D2, deliberately balanced to be very good for PvE.
There could also be a quest that's started by equipping all of the Destiny 1 gear, it could involve going back to the Cosmodrome.