Having TA'ed engineering undergraduates, I have serious reservations about whether the bottom third or so of most classes can walk and chew gum at the same time, let alone go on to a career where they don't get anybody killed though an ill-placed screw-up.

The last thing we need is further inflation of admissions to put more bums in seats. There are probably already more people in STEM programs than properly have the actual aptitude for it.