when you wear then you're not completely covered up and your face is still very much visible. you're not protected from the atmosphere and it doesn't have an internal air tank. it can only carry much less than an actual mech can. it puts you at a set speed that is slower than human run speed but faster than a RIPLEY's normal speed. you can still pass through people and don't block the view of things behind you (in other words, you lack the density that a mech has.)
basically this would allow convenience mechs for much of the crew. a book stocking mech/botany mech/janitor mech would actually be feasible if it wasn't a giant dense stompy machine, but rather a thin bunch of latices that wrap around you to allow you to use heavy tools.
as you can see in this image of an actual RIPLEY from the movie...
![Image](http://static.comicvine.com/uploads/original/10/104794/2258596-aliens_ripley_powerloader_1196993715.jpeg)
this man is not inside some giant dense impassable block of metal, he is covered in a bunch of metal bits that let him use giant clamps, and nothing more. no armor or excessive tools or personal atmosphere with spaceworthiness on top. just a clamping suit for clamping things. this is essentially what i am proposing, except that it would not be limited to clamps.