I'd like to see bonuses on raid/ trials armour sets dependant on the number of parts of the set you are wearing.
One idea along this line is that perks such as the current raid-weapon perks are applied with armour to any weapon. Take the King's Fall weapon perk Cocoon for example. Instead of this being on all the King's Fall weapons it is applied based on the number of King's Fall armour items you wear.
2-set: The cocoon perk is applied to your equipped heavy weapon.
3-set: The cocoon perk is applied to your equipped heavy and special weapon.
4-set: The cocoon perk is applied to all your equipped weapons.
For the VoG armour, this could have applied the oracle disruptor perk in a similar fashion etc.
Having the perk from 2-set means you could mix and match two perks onto a heavy weapon if that works.
Obviously this is just an example, the options are endless and unlikely in Destiny 1, but for Destiny 2 I'd love to see something along these lines. Full credit to my memories of WoW and collecting their raid armour sets!