I think the guardian and his ghost should talk. It's a lot of missed opportunities to help the plot along..explain what's going on in a given scenario, provide helpful tips, or introduce lore info into the game. 2 games that did this well are Last of Us and Tales of Symphonia. in LoU the guy and girl would have conversations while heading to the next destination and she would tell him to watch out for certain things. in tales of symphonia you could talk to members of the group and they could talk to one another. of course all of that couldn't transfer to destiny well but even introducing synergy with ghost that come with small perks like quicker revive or something.