I have a question regarding this and Subtlety rating. This sidebar states:

Some characters may wish to apply their weapon modifications personally. If a character decides to do this, he gains a +30 bonus to the modification’s Availability when making the requisition test to acquire it.

Does this mean that Availability of the modification is changed three steps up and, in turn, doesn't cause a penalty to Subtlety (or, at least, causes a lesser penalty) or is it just a bonus to the requisition check?

The reason I'm asking is because other similar examples (such as The Emperor Provides) specifically state that they provide a bonus on the Requisition check, whereas this gives a bonus on Availability, so I'm trying to figure out if there are differences.

Alright, my opinion is that a bonus and a decrease in difficulty are two very different things. I'm going with "it is just a bonus to the requisition check". Otherwise, you get things like Exterminators becoming Ubiquitous. You see how that can get wonky pretty quickly? See also: Adeptus Administratum characters getting weapon modifications at four levels more Available than normal.