Every ERA manufacturer in the world want to reduce blast and amount of shrapnels in case of ERA brick explosion, and you would want to do everything in reverse?
You know that ERA even without your modifications is still very dangerous to the tank's accompanying infantry.
No need to make it even more dangerous. It's more effective and feasible to have accompanying infrantry, rather than lone tank with some pretty useless ERA against tanks, and disputable effectivness against infantry[claymores have like 100m effectivness] It's better when tanks have some canister rounds.

The modified ERA panels could be designed in a manner such as the Claymore AP mine utilizing the Misznay-Schardin effect, especially in a tank as well armored as the Abrams or Challenger 2 for that matter to focus the majority of shrapnel and blast outwards.

I fail to see how it is backwards, they would be command detonated, or set off by an impact from a warhead using a explosively formed penetrator round/rocket. Thus if they shoot at the tank it would be set off by impact like normal ERA. Just with more shrapnel, which in tight urban combat could very well take out the asymmetrical warfare guerrilla forces that would most likely be firing RPGs at the tank/APC from close quarters due to the confinement. So as bad as it might seem to some of you I feel that any injuries to non combatants would be solely the fault of the person attacking the Abrams.

The Abrams does carry canister rounds, but in a tight urban environment it is not uncommon to get in a area were the main gun can only be rotated a total of say 25-35 degrees total. Knowing that do you think the attackers would charge in dead ahead of the tank? I seriously doubt it, they would want to press every little advantage they can muster to have a chance of disabling the tank. So a flanking attack from both the sides and rear would be there most effective ambush tactic I.M.O. Not to mention that the Coaxial gun would also be rendered useless by not being able to rotate the turret freely.

Keep in mind I'm not trying to say that it's a perfect concept, and I'm am in no way implying that this would be a primary defensive weapon. It is just another layer of protection and most likely would be a last ditch weapon but I do think it has the potential to save the lives of our servicemen. Not to mention as I said if the modified ERA panels could be made to look exactly the same as standard ERA panels it would multiply effectiveness by helping spread fear and uncertainty to an otherwise very determined enemy combatant.

I appreciate the input, both the positive and negative, I try to run these kinds of scenarios/hair brained ideas and I love bouncing the ideas off of fellow weaponry wackos.