I think the best multipurpose replacement for the Hydra is going to be the Quad Gun, probably with the Aegis defence line. It's pretty cheap and you can get a squad of 3 Ratlings to hide behind it and fire it with BS4, all for 130 points and providing 4+ cover for a sizeable unit of Guardsmen.
e: I think Ogryns took a hit with the challenge rules. They need to be babysat by somebody and if you use a Lord Commissar he's going to be harassed with challenges and if he refuses you can't use his leadership. You could do pretty well escorting them with a Space Marine character geared up for survivability, I suppose.