Regarding the "input-block", if the goal is to fill the space, we could leverage the presentational semantics that already exist in grids.  This would also provide a way to reintroduce the various input sizes without adding new semantics.

I'm thinking something like:

```css
.yui3-input-1-1 {
    width: 100%;
}
.yui3-input-1-2 {
    width: 50%;
}

.yui3-input-1-4 {
    width: 25%;
}

```