Yes Glow Heads lol!
The Poison thing I never had a problem with in FFR because sex change or not she could still like Cody. Yes you are right that COJ has never acknowledged that aspect of Poison though, if he/she could like a man. Yeah, some of those images that happen during Poison's Kiss Super Art might be difficult without the sex change but there's always tucking between your legs and tight underwear so...
The Zombie Belger ordeal was always the most difficult thing for me to swallow. He can throw his head at you, it can blow up and he can regrow a new head! I don't know how many zombie laws are broken right there, how can you regrow a new brain?

I mean, Akiman just drew regular Belger for his portrait, he didn't even draw zombie Belger! What character in any fighter doesn't reflect his portrait at all? Crazy crazy Capcom USA...
I do find it funny because online and even in real life I've met a few Capcom fans who believe they have some kind of 'secret knowledge' for the reason why Cody went to jail from Final Fight Revenge. Even though all you need to know is in SFA/Z 3. It's not even that they particularly like FFR, maybe they want to justify their purchase, I dunno. It's bizarre though. When it comes up I usually say "Yeah but Zombie Belger? C'MON..."
At least everyone automatically tosses out Mighty Final Fight. Probably has more to do with Chibi characters than Cyborg Belger...
On Capcom USA's site they have poked fun at Final Fight Streetwise quite a few times in Blog entries and posts over the years. This is after Team Eight went the way of the dinosaur and all. It will be really random for me to find examples, and sometimes jokes are just jokes that don't mean much. I have gotten the impression that Sven and co. don't care for it over the years. Not that it particularly means it will get erased, of course.
Capcom USA still has the license for Final Fight though, but again Capcom rarely erases entire games from not happening at all AFAIK. If they make another FF game it will probably take place before Streetwise.
In theory they can always put something in SSF4 that removes it. All it would take is Cody saying "What are you talking about? I don't have a little brother." and that would be it.
EDITED A BUNCH OF TIMES. IN A RAMBLING MOOD I GUESS...