I just don't like the idea of stalling Bigras/Zadorov's jump to the nhl that much longer.
This is the point you are missing in what I am saying here. The addition of a 4/5 RD would speed that process up. That player can help Bigras get accustomed to the NHL and get him bigger minutes, sooner than if he is saddled with Redmond or Guenin. Nor do I see anything in Holden's game that shows he can carry Bigras when Bigras is having some issues.
Holden may be the casualty of this, but the sooner that Bigras and Zadorov can get established, the sooner the defense can be a strength of this team and not a patchwork.
At VERY least, the Avs should upgrade the extra RD spot that Guenin and Redmond occupy. That way when injuries to happen, they can have a competent player consistently with Bigras. If I was the Avs, I'd be trying to package Siemens with a pick to land a RD in the 22-25 age range who is fairly established in the NHL.
I can say there is a side to side difference with a number of defensemen, many prefer one side or the other and mostly it goes by handedness. Having only one right shot defense would also limit the way this team can play in every phase of the game. Breakouts are different, PK pairings have to be different, the PP has to be setup differently (especially with the Avs two best PP defensemen being right shots). Holden has played the right side before... he has never played the right side at an acceptable level in the NHL.