It would fall to GM discretion, because you'd be creating a custom magic item.
That said, it is a pretty straightforward task to figure out what the flat magic ability cost of the reduction in ACP and charge ability is (seperating them could be a challenge, though; I'd take it at an all or nothing).
It appears that a 2 better ACP plus an addition 2D6 on charge (the Rhino Hide effect) would cost 1000gp (market price) to add to enchanted armor. 2 better ACP and +4D6 on charge (a couple of the versions of Mammoth armor's effect) would be 2500 additional market value. Oddly, the +3D6 version of Mammoth Hide (from Melee Tactics Toolbox) adds 4000 to the market price, so I'd avoid that one.
As a DM, I would rule against making a rhino or Mammoth version of a different armor.
One of the aesthetic shortcomings of PF and 3.X generally is that there's generally no incentive to use anything lighter than breastplate for medium armor classes or full plate for heavy armor classes. This is ahistorical for anyone who's really into arms and armor (I know, this isn't a historical game. Shoot me.) Beyond that it's kind of annoying to imagine all warriors dressing the same.
So when Pathfinder gives us a specific hide or scalemail with magical qualities that make it competitive with full plate or breastplate, I prefer that the individuality of that armor not be tampered with.
I could see a GM making a gorgon hide field plate (or other non-fullplate heavy) version available for the reason the OP wants but still in keeping with Zolanoteph's reasoning for wanting to limit the types of armor it could apply to. Not only does the flavor break when speaking of using ordinary steel (or other metal) armor, but it can be nice to add variety by forcing choices.