I think it would be nearly impossible to do well, so we shouldn't so it at all. The main problem I see with it is that it is a really hard thing to actually find out. If the armourer for a production is credited, it will generally be the on set armourer and not the prop house that provided the weapons themselves. For example a pretty good indicator or something that "The Specialists LTD" are involved with is those SG 550/P556 hybrids that turn up, and if you look at the IMDB pages for
Salt and
Jack Reacher you will see that the armourer is credited as Sam Arthurs. However he is not credited for
Burn Notice where it is John Patteson. However, in the latter case he is only credited in 17 episodes, so either they didn't bother crediting him for some episodes, or the armourer was different for different episodes. In some cases there is not armourer credited at all, such as
The Blacklist which uses weapons from "The Specialists LTD".
Another thing is that films and television series often have different filming locations possibly spanning multiple countries where the weapons would most likely be provided by different companies. A good recent example of this is
season 4 of Strike Back, where as they move to different countries you can see that the weapons completely change as the company that provides them does likewise.
Even if you did positively identify a production which has weapons from a specific prop house, it may be the case that they didn't provide all of them. For example I believe that
Boardwalk Empire has some weapons provided by "The Specialists LTD", however there are a lot of the more esoteric period weapons that are not listed on their site, which would lead me to believe that there were other sources. In my opinion it is better to give nobody credit for something that to give it to the wrong people.
At the end of the day, we would probably only be able to positively ID the weapon provider for a very small percentage of titles meaning it would be ridiculously incomplete, so it really isn't worth doing in my opinion.