I think there are a couple of problems with the idea.
(1) The first is pretty simple: Steve has already said he doesn't want to do this. Especially since C# which has made a big goal of eliminating the "special cases" that characterized VB6. This is also why we do not have PDCs anymore as they were considered a "special case" of ships, so it is perhaps not a victimless philosophy, but it is the philosophy Steve has chosen to move forward with. Adding a specific module with specific rules exceptions to enable a specific type of ship to be built is not really in the spirit of Aurora, where every other component type can be used in many different kinds of designs allowing emergent fleet doctrines and the style of gameplay Aurora excels at offering.
If we want to build small fighters, the direction Steve has been taking this is evident from the recent introduction of reduced-shot railguns, which have enabled us to build sub-100 ton beam fighters while remaining roughly in line with existing mechanics - although these are of course not as efficient as larger fighters or ship-mounted weapons, generally. This is I think a more preferable approach as it adds an additional design mechanic rather than an exception to the rules, although it admittedly doesn't extend to the other weapon types as there is not such a thing as, e.g., reduced-shot lasers to be added.
(2) Secondly, the "fighter module" as proposed is quite overpowered. The comparison you've made to CIWS is instructive; I've recently done
an analysis comparing CIWS to standard components, and for being a "self-contained" weapons system the gains are nontrivial but still fairly modest, with about ~1 HS of weight savings from assigning 5 HS to the twin 50% Gauss cannons instead of the standard 6 HS, plus smaller savings from reduced crew and BFC range requirements for the design specification. Of note, the BFC itself is exactly the same as what you can design yourself using the single weapon (SW) option as of 1.13 - any savings from BFC size are solely due to the SW qualification and the 40,000 km range (where most players will use a longer range for their PD BFCs especially at higher tech levels), but it is exactly the same as if a player designed it with those parameters and there is no longer a unique exception.
By comparison, the kind of system being proposed here goes way beyond the limits of game mechanics. The BFC is the easiest example, as the indicated specifications would be at least 25 tons at the base tech level and only dropping to ~5 tons at the 96,000 km (30k RP) tech level - this is assuming a BFC range of 10,000 km, although mechanically I'd expect something closer to 40,000 km like for CIWS to allow reasonable hit chances particularly in final fire PD mode. More egregious is the specification for the Gauss cannon; at 3x the racial ROF tech level, the 4% accuracy is nearly equivalent to a 'standard' 12% accuracy Gauss cannon (0.75 HS), and you are proposing to cram this much firepower into 0.2 HS
with an integrated BFC.
This means that, even if the concept of a "space superiority fighter" is otherwise useless (which I am not saying that it is), we can stick these 0.2-HS weapon suites onto a fighter body with, say, a 0.2-HS engine with max boost and 1,000 L of fuel, giving us a ~30-ton (0.6 HS) point defense "turret" for about half the effective size of an equivalent Gauss turret once gearing and BFC size is factored in. In other words the proposed component would make basically any other kind of beam point defense more or less obsolete - granted, this is with the caveat that we need clarity on how the BFC and combat range are actually set, so here I am basically assuming a BFC range of 10,000 km and a combat range of 1,000 km in line with the given specifications.
If we are going to do something like this, I would rather see a module which (i) follows the SW-BFC rules just as CIWS, STOs, etc. already do, so there is no exception in the rules, and (ii) functions similarly to existing weapon types in terms of rules with a meaningful benefit tied to reduced or limited performance, as CIWS does. There's a few possibilities we could consider for reduced-size weapons - increased weapons failure chance, box launcher-like explosion chances, and so on - which I think would add interesting design decisions without making a big exception to the rules, and could even if well-implemented become options for larger ships as well.
