2010/2/16 Manuel Pégourié-Gonnard <[log in to unmask]>:
> - the very core of the kernel using only features common to pdfTeX, XeTeX and
> LuaTeX (perhaps with some emulation, such as implementing pdfstrcmp in Lua).

Then this very core will be implemented in the greatest common
divisor, i.e. 8-Bit eTeX, while the rest of the TeX world will use all
the features of LuaTeX - i.e. Lua. What do you hope to gain here?
Compatability with an engine whose basic concept is now 32 years old?
So we have to cope with e.g. \expandafter for the forseeable future
(for some of us, probably the rest of our lives), instead of using a
clean approach, i.e. a real programming language (Lua)?

IMNSHO LaTeX3 would be a chance (probably the last) to burn some
bridges and start with a much cleaner slate.

And if LuaTeX is not really the engine you want: Fork it and make it
what you need.