That all sounds very plausible, though I hope that the UI limitation isn't real in this case. In regards to original reasons for the title restrictions, I'm guessing its a matter of "it seemed like a good idea at the time".
In this image I borrowed from Paragon WIki, we can see a list of titles available to this particular character. We also see a scroll-down function, which implies that the list could be extended. I'm obviously not an authority on the CoH UI, but this gives me some hope that more titles could be added.