There are a few ways to try to do P-1 only.
there have been attempts to do P-1 in a semi-auto mode. See this
http://mersenneforum.org/showthread....1671#post11671
There is more discussion here.
http://www.mersenneforum.org/showthread.php?t=2266
What you are talking about is not pointless. As a matter of fact, there are several folks that are trying to "clean-up" all exponents that have had 1 L-L, but weren't P-1'ed. This can help save DC'ing time. With lots of RAM, you could help. Look att this subforum
http://mersenneforum.org/forumdisplay.php?f=30