There are several functions in the various CS programs, that directly rely on the OS, and its method of handling things. This might be via the fonts, installed into the OS, file Saving dialogs, file Opening dialogs, and some others.
Adobe has chosen, that than write their own functions, to rely on those in the OS already.
Now, I can see a benift of arranging fonts, within the CS programs. I could use that in PS, Illustrator and InDesign, mostly, and admit that it would benefit me to maybe NOT display all of the ~ 350 loaded at any one time, in Titler, since I probably use only about 10 with any regularity. However, that would require some re-coding, since the font list display comes from the OS.
To get around sorting through ~ 350 fonts in Titler, I have just created Styles, for my common fonts, and the normal treatment, that I apply to them - not perfect, and not as clean as your suggestion, but it works fine for me, with Adobe's reliance on some OS functions.
I would offer support for a Feature Request, but not sure how far that would go, and how many resources would be required to cut the "umbilical cord" with the OS. I worry that those resources could be better spent, fixing some things (spanned Clips comes to mind) in PrPro.
Just my observation,
Hunt