Class A motorhomes in particular are so poorly supported and reinforced on the front end that you would need a carload of steel to build a decent structure far enough back to find support for anything that could even pretend to perform like a cow catcher. The best approach is to double drive defensively and definitely don't follow to closely. In addition to all that it would probably be necessary to install additional springs or airbags to hold all that junk up. And then what would all that do to the GVWR?