> Modifying TeX to accept utf as input (I mean the compiler/interpreter by
> itself; not macros), converting to rune and then using 16 bits � la math
> mode to switch inside a font family to the "correct" 256 vector is
> something that, for a first step, seems to me both reasonable and
> simple.

What about XeTeX?  It is a merge of TeX with Unicode and
modern font tech.  Works with OpenType Fonts.  Included in TeX
Live among others.  I can use XeTeX with TeXShop & TeXWorks. I
am just a user so don't know how hard it would be to port but
seems like it is widely used now.

See
    http://scripts.sil.org/xetex
Some more examples @
    http://nitens.org/taraborelli/latex