Well, my issue with Steam about my username has been resolved. After you guys spread the word - via Twitter, journal posts, and even Reddit (twice), a support person replied to the ticket I quoted from in my post to tell me that I could create a new account and they would transfer the games from my old account to my new one.
This is a great outcome, and I want to thank Valve for allowing this to happen, as well as everybody who spread the word, thereby bringing it to Valve's attention. I've now created the new account and the games have been transferred over, and they seem to work fine - in particular, one of the games I expected to have issues with (GTA4) has had (so far) no issues at all, despite its SecuROM protection and Games for Windows LIVE setup. (I did get issued a new key to use for it, but I expected that, since I was effectively a different user.)
( I also want to respond to some of the stuff that was said about me by others. )
One thing I asked in the ticket after all this happened was whether there were any plans to change the policy, and I suggested that Steam could allow it for people who have legal name change documents, which should pretty effectively prevent fraud or ban/VAC evasion. Their reply was, and I quote:
We appreciate your suggestion, however I have no information on upcoming Steam client changes or updates.I've asked that the suggestion be submitted to management, if possible. (I'm assuming that they didn't actually mean *client* changes or updates.)
So, it seems that this was likely a one-off, especially as they didn't actually ask *me* for my legal name change documents. I do hope that they change their policy, though, because I suspect I'm far from the only person in this situation.
Thank you to everybody who spread the word about this, and thank you to Valve for a quick, helpful response! (Although I wish I hadn't needed to get it this way.)