I have an old lawnmower.  I have removed many parts from it.  It works
better now.  They were mostly broken but not necessarily superfluous.  In
any case I deemed them to be unnecessary and interfering with the main
function of the machine--to mow the lawn.  I even turned the engine sideways
because I determined the throttle control cable was binding due the to right
turn it had to make.  It works better now.  This is not to say that the
battery cover does not perform some function as you pointed out.  I assumed
that it does.  But it was interfering with my routine maintenance so it's a
goner.  I have to clean the battery terminals anyway.  And that brings us to
the red plastic cover over the positive terminal.  It seems to me that it
traps acid vapors and *causes* the terminal to corrode much more quickly.
Sure, it prevents idiots from accidently shorting out their battery by
setting a wrench across the terminals, but I still say it causes other
problems.  I still have my red plastic covers, but I don't know for how
long.  I don't know why Ford or whoever does some of the things they do but
I suspect some things were imposed upon them by the government because some
politician was working on his own car and did something stupid so now we
have a new law.  One of the reasons I like my old '91 Exploder so much is:
no air bags.  I can easily imagine a situation where I bump into something
on a mountain trail, the bad inflates and I go over a cliff cause I can't
see.  I also recently found out that my car insurance is lower if you don't
have anti-lock brakes.  Why is that?