To speak the truth, I think it's quite a waste of time to try
implementing inputenc and fontenc in LuaTeX,
It is not a waste of time if we ever want "latex" (as opposed to just
"lualatex") to invoke luatex instead of pdftex. Which is an extremely
desirable goal, IMHO. To achieve that, luatex has to be utterly
compatible with existing documents in the real world.