3. Christian Parker
Parker technically would not be an addition to the Broncos considering he is currently employed by the team, but after the departure of Ejiro Evero for Carolina and the installment of Vic Fangio as the Dolphins' defensive coordinator, there are definitely a few worthwhile connections for Parker around the league that could lead to his departure. He has worked for the last few years as the defensive backs coach for the Broncos and recently may have interviewed (not confirmed) for the Broncos' DC position.
Parker is only 31, and the position he holds now is the highest he has held in any capacity in football, but he is widely considered to be one of the brightest young defensive minds in football and is seen as a quick riser in football. Piecing that together, it feels as though it is only a matter of time before Parker becomes a defensive coordinator, and he may just get that opportunity in Denver under Sean Payton.
Parker, as was mentioned before, is one who could have plenty of options around the league should he leave the Broncos. While he would not technically be an addition for the team, he is likely the most important name to retain who is still on the staff. An ideal situation for them could be a scenario where the Broncos bring in a veteran defensive play caller, maybe someone to the tune of a Rex Ryan, and let Parker learn under an established, veteran play caller before getting his chance in Denver.
Parker should be in no rush to rise to a top spot, especially considering his career trajectory puts him on a path to get more than his fair share of shots, A scenario where the Broncos let Parker learn under a strong system before becoming the top guy offers Denver a chance of immediate success while setting themselves up for long-term success and continuity. If the Broncos could retain Christian Parker and keep him from moving on to a new stop, that would be a major win for the franchise and for the long-term health of Sean Payton's defensive staff.