Rumour has it that there is to be an option to automatically be pinned to take a cover save against attacks.

Our own house rules have been that anyone can claim a light cover save for being prone. The only clincher is that you have to have them modeled prone. I have a squad of space marines all crawling or lying down, and our house rules are basically that you can get the cover save if you are prone, BUT you cannot initiate close combat, nor can you sprint or make fleet moves.

It may not sound like much, but there have been games where that save has made the difference between victory and defeat.

Plus, the models look really cool, and make for an interesting conversion project. (which any army can do)