(Just want to say before I start arguing that I don’t mean to be combative - I just find this interesting and want to think it through. I’m also a law student, so I’m interested in thinking through the viability and consequences of a hypothetical law like the SHRA.)
(Speaking of which, this also all heavily dependent on the specific terms and requirements of the SHRA, which were never consistently outlined even in the original Civil War storyline.)
I do agree that Injustice and Kingdom Come, while superficially similar to Civil War, are about a different kind of dilemma. That said, I still don’t buy Superman supporting registration, or several of the others on Etrigan’s list (again, no offense, I just want to think about it).
First, Supes (particularly in regards to Truth_of_Pisces’ point): Keep in mind that the Dark Knight Returns is (a) a dystopian alternate future and (b) a Batman story. Superman is a government stooge there because it sets up a worst case scenario for Batman, not because that’s Superman’s “normal” characterization. Also note that if Clark Kent “had faith in the system,” he wouldn’t need to be Superman any more than Bruce Wayne needs to be Batman. He’s got a more public persona than Batman, but he still disguises himself and works outside of any legitimate authority. And of course, both of them have at least enough faith in the system to trust their villains to the normal criminal justice process no matter how many times they break out. Indeed, Superman’s got the most dangerous villains, so if anything, he’d be the most threatened by having to register and trust the safety of his identity (and, by extension, the safety of his loved ones) to the government. Which, of course, is known for its ability to not have secret information be leaked.
Hal (and to a lesser extent John) does not have much patience for Earth-based red tape when he’s trying to get his job done. The Green Lanterns in general consider themselves above any specific terrestrial jurisdiction. Look at the early portions of Geoff Johns’ run and Hal and John’s dust-up with Black Adam in 52. So, I really don’t see any of them going in for registration. Least of all Guy, though I assume that’s a typo since he’s on both lists.
The other one on your list that I find very curious is Nightwing. As a member of the Bat-Family, I think he’d have a lot of the same concerns as Batman, and for a lot of the same reasons. On top of that, his connections with the Titans mean that he’s got an interest in making sure they don’t get screwed over by the act. What would the government do if they knew who Raven is and where her powers come from? What if Wally had to unmask? What if they found out about Roy’s history of drug abuse? Nightwing would be betraying two different families by going pro-reg, and to what gain? To support an act that puts him in as much danger as any of them and doesn’t actually accomplish all that much in the DC Universe?
Actually, that’s another point: the DC superhero community polices themselves much more rigorously than the Marvel one, and most of the young heroes are under the direct training and mentorship of more experienced ones. There’s less chance that an incident like Stamford would happen, and less need for the government to do something that people like the JLA already have a vested interest in keeping under control. Plus, the public already trusts their heroes a lot more than their Marvel counterparts. That means the SHRA would already have a lot less popular support, and might not be passed to begin with.
Oddly, on your anti-reg list, I think there’s actually a convincing argument that Green Arrow would be for registration. He’s always supposed to be the champion of the little guy, and so his position would depend on who he actually sees as the “little guy.” Maybe he’d think the superheroes aren’t accountable and the “little guy” is the people like the kids who got blown up at Stamford, and the superheroes are the “fat cats” by comparison. That sort of thing is exactly why he’s usually written as very reluctant to work with the Justice League. Now, I think even he would see what an overreach the SHRA is, but one could sensibly write him as supporting it.
If I wanted to write a DC version of Civil War, I’d have to assume the act’s provisions are fairly mild and interpret characters as generously as possible to bolster the pro-reg side. I’m also splitting some characters who’d more likely be on the same side for drama’s sake. I’d draw up these battle lines (also non-comprehensive) :
Batman (For the reasons I mentioned in my first post - might change sides)
Martian Manhunter (unlikely, but he could be interested in the safety of the country/planet over that of the superhero community)
Aquaman (Again, I think he’d stay out of it, but I’ll give you this one for the sake of argument)
Green Arrow (See above)
Elongated Man (Would probably side with Barry regardless)
The JSA (I don’t necessarily see this happening, but it seems more plausible than splitting the Titans, and I needed a similarly powerful team on this side to balance them out)
All Green Lanterns
Blue Beetle (any - Ted might go pro-reg, though)
All Bat-Family other than Bruce and Kate