If we're going to get anything done, we'd likely need incremental improvements (or real strong motivation). Yes, four passes is a little more complex than we'd want, and would make the grammar a bit unwieldy. But it's not complex or unwieldy enough to handle all of the corner cases in the current parser. So it would at least be a step in the right direction.
If incremental improvements was going to work, we'd have done it by now. The parser is such a mess that we really need to bite the bullet and just do it - incremental improvements isn't going to cut it.
(And when I say "we", I mean those us of know what EBNF stands for without looking it up, which doesn't include me. ;))