Question: Is it possible to uglify all the RequireJS modules without concatenating them into a single file? (I know the other way round is possible with `optimize: "none"`).

Answer: 
Material UI have implemented their own Flexbox layout via the [Grid component](https://material-ui.com/components/grid/). 

It appears they [initially wanted](https://github.com/callemall/material-ui/issues/3614#issuecomment-193119929) to keep themselves as purely a 'components' library. But one of the core developers [decided it was too important not to have their own](https://github.com/callemall/material-ui/issues/3614#issuecomment-250996378). It has now been [merged into the core code](https://github.com/callemall/material-ui/pull/5808) and was [released with v1.0.0](https://github.com/mui-org/material-ui/releases/tag/v1.0.0).

You can install it via:

```
npm install @material-ui/core

```

It is now in the official [documentation with code examples](https://material-ui.com/components/grid/).
I hope this is not too late to give a response. 

I was also looking for a simple, robust, flexible and highly customizable bootstrap like react grid system to use in my projects.

The best I know of is `react-pure-grid` <https://www.npmjs.com/package/react-pure-grid>

`react-pure-grid` gives you the power to customize every aspect of your grid system, while at the same time it has built in defaults which probably suits any project

**Usage**

```
npm install react-pure-grid --save

```

-

```
import {Container, Row, Col} from 'react-pure-grid';

const App = () => (
      <Container>
        <Row>
          <Col xs={6} md={4} lg={3}>Hello, world!</Col>
        </Row>
        <Row>
            <Col xsOffset={5} xs={7}>Welcome!</Col>
        </Row>
      </Container>
);

```