This was answered in a Support Ticket on May 30, 2014 but I thought it was worth including here on the Forum for others with the same question.
I can understand your frustration in the apparent conflict between having Chrome Enterprise in Pro and Firefox ESR in Enterprise.
We determine the Package Library level based on a number of factors, a big one being the complexity involved in writing and maintaining the package. The Chrome Enterprise package is relatively straight forward and only requires two steps to install. The Firefox ESR is far more complex requiring 8 steps to install. It also requires the creation and placement of the mozilla.cfg file which can be tricky, especially if an existing cfg is in place on the target.
It takes quite a bit of time when new releases come out to verify that the install is working and to determine if all 8 steps are still required. Because of this we are going to keep the Firefox ESR in the Enterprise category.
Please keep in mind that you can create your own packages. You are not limited to what we have in the library. We do not use any special tools to create our packages. Most of our time is spent researching the proper methods for silent installs.