Your initial belief is correct. The TT and PS hints are closely linked to the outline formats, so there is no way to apply TT hints to a PS outline.

The instructions and glyphs are actually mixed into a single table, which is one of the first things the next format should address. If we ever get around to it, some will probably want to eliminate the instructions altogether, and others will want to eliminate the glyphs altogether. :-.

Cheers!

If we ever get around to it...
I would like to be able to put many design sizes inside the same font, along with some kind of specification about when to use which.
Could this somehow be added to the .webfonts proposal?

I have elaborated my ideas here.

My suggestion is directly related to the approach shown by David Berlow in Screen Fonts: An Abbr. Hist., and to my own work on the Elementar bitmap font system (some images here).

I would like to be able to put many design sizes inside the same font, along with some kind of specification about when to use which.
Could this somehow be added to the .webfonts proposal?

No, but it could be added to the composite font format standard, which is being developed. There is support from at least some participants for using this format for different size-specific fonts within a single composite font.

Thanks for the feedback, John. I would love to know more about this proposal and collaborate with ideas and/or prototype fonts.