Long Live the Confederation!
One way or another, I’m fairly certain that the CF designation doesn’t represent a manufacturer; rather than adding an X designation for experimental models, Confed appears to use letter designations pertaining to the company manufacturer, similar to American manufacturer's codes used during World War 2.
I don't follow you, I'm not aware of any reference to a WW2-USN-style system for Confederation fighters ordered by manufacturer (there is one for Border Worlds fighters, but it hasn't been published.)
The Confederation *does* seem to use the same status prefix designation system as the US military -- we see the YA-18 Crossbow in Special Operations 1 (contrary to popular opinion, 'Y' means prototype... 'X' means experimental, and you would not fly an experimental spaceframe in combat.)
However, the one problem with this is that while the Broadsword was reclassified as A-17, later Attack craft such as the Raptor (A-14) and Gladius (A-15) receive lower numbers.
That's not really a problem, though -- there's nothing preventing the Raptor and the Gladius from being older than the Broadsword.
To address the subject, though, there are three obvious schools of thought:
1) The systems are SEQUENTIAL
2) The systems are CONCURRENT
3) There is only one system
Under (1), I see two possible explanations:
a) One system replaces the other
b) One system follows the other
Both of these are based on the 'real' designation shift from the 1960s. Option (a) would be the shift from the Navy to the unified system -- the old system was simply thrown out entirely (no more PBJs, TB3Ms and so forth) and replaced with a new type of numbering. (b) would be the Air Force's experience... which essentially amounts to a renumbering starting back at 1 (ie, CF-337 Stryker is followed by CF-338 Crabhammer is followed by F-1 StarLancer.)
System (2) is the easy answer -- that every military contract spaceframe has a 'CF' designation that's separate from its US military-style designation... so the F-109 Vampire might also be the CF-883.)
... and then system (3) is that there's only one system which for whatever reason has given unusual 'CF' designations to several spacecraft, separating them from ordinary fighters (F), attack craft (A) and so forth. This is not entirely without merit -- look at the F-117 today. It is possible that these spacecraft all share some common merit that gives them this unusual designation... and that the Broadsword has concurrent designations similar to all the revamps of the B-17 or the B-29.
Now, we don't have an answer for this yet, but in considering it we might want to remember that the designer's *intentions* were more along the lines of #1 (or #3) than #2 -- the 'CF' was supposed to be the same type of designation as seen in the other games, just not as well developed.
And then towards suggestion 3, note that the Kilrathi 'KF' designation system still seems to be in use for fighters we're familiar with later in the games.
(Also, in considering the CF-337 remember that these don't *necessarily* have to be linear. Think of the German system in World War II which would make the followup to the ME-110 the ME-210... the CF-337 might be an update of the CF-237 and the CF-137 and so forth. There are always possibilities...)
If there was some great change over in Confed’s spacecraft designation system, it appears to have taken place sometime between 2632 and 2633. This would mark the time that the Broadsword was reclassified A-17 (though if the movie material is any indicator, the CF-131 designation remained until at least 2654) and the introduction of the F-10 Merlin.
The mistake here is assuming that there is a precise cutoff between the two designation systems and that the material we see will immediately reflect it. Almost any history, including one printed today, will refer to the Mustang as the 'P-51', even though it ended its career as the F-51 thanks to a similar reboot...