DHClient

There is a lot more using env rather than environment for module names.
Plus there is already a auxiliary that does mostly the same (just doesn't use /etc/crontab):

$ find modules -name '*environment*.rb' | wc -l
       2
$ find modules -name '*env*.rb' | wc -l
      30
$
$ find . -name 'dhclient*'
./modules/auxiliary/server/dhclient_bash_env.rb
$

PXE

Making sure their names match as they are mostly the same with:

• exploits/windows/local/pxe_exploit
• auxiliary/server/pxe_exploit

At the same time, rather than it all being a single word, separating them out with _

Shellshock

• Variable Injection -> Variable Code Injection
• Making sure (Shellshock) (aka the codename) is at the end