Two more calls today, not much progress to report, but hopefully a few useful pieces of information for others. Transferred to the tech team both times upon my insistence (second time I just asked for the transfer immediately - politely but without hesitation - and got it with no issue). I think including that request in my "subject" line for the second call was also helpful.
Back to the first call - First tech team member had a thick accent (accompanied by lots of background chatter) so she was hard to understand and seemed confused. She refused to speak to one of their higher-level "specialists" (seemingly others have called those same people "consultants," but I think the right way to refer to them is Tier II). She repeatedly tried to read off of scripts and tell me there was nothing anyone could do, so I just told her I'd open a new case to get a call back from someone else.
For the second call I specifically asked for a tech team member without a heavy accent. Maybe it was just luck of the draw, but I got an Aussie, so that was fine (doesn't hurt to ask). He confirmed that there's a "Studio" group. Apparently, there are three levels of reps who actually get involved when you call: (1) the initial reps (VERY basic knowledge and scripted answers), (2) the people EA reps commonly call the tech team (who handle Tier I problem cases and also rely heavily on the scripted answers but have limited additional knowledge), and then (3) the consultants/specialists (who handle Tier II tech team cases). Allegedly (not sure I believe this based on others reporting success from just a 20-min call and what Christian B told me yesterday morning), even those Tier II people can't put characters into your game because they don't have all of the same tools as the Studio Group. Either way, I was told I needed to continue to wait and it could be 24-72 hours or up to 5 business days until I get an email response from the Studio Group.
Since my case was escalated on Monday, I guess now I wait until Monday afternoon before calling yet again. Telling me to wait has become the standard answer from all levels of support (despite other players reporting this as being a very quick fix if you get the right person).