There is nothing wrong with the current layout rules[1]; they don't need to change.
[1] Regarding tabs, that is; there *is* a problem when you start dealing with characters which aren't necessarily "one character cell" wide (e.g. CJK).
Note that the revised Haskell 98 report contains this paragraph (section 9.3), which was added as a result of previous discussion on this topic: For the purposes of the layout rule, Unicode characters in a source program are considered to be of the same, fixed, width as an ASCII character. However, to avoid visual confusion, programmers should avoid writing programs in which the meaning of implicit layout depends on the width of non-space characters. I think this is all that is needed. Cheers, Simon