Point by point:
Thanks for zooming my eyes on the flechette part, i had skipped it for some odd reason.
I will also playtest this in my group. Look at the changes:
As per Rulebook
Belzarachs: CC:0 DAM: ST
Invader: CC: -4 DAM: ST
Both are pretty crappy weapons in CC due to the pathetic damage, but the belzarach was still much better. The increased CC also explained why it was a largely inaccurate weapon for shooting.
The reason for the Belzarach being inaccurate is two-fold:
a.) It is little more than a heavy sub-machine gun, not truly an assault rifle. It is listed as an assault rifle mainly due to its damage, and its lack of multi-round fire at shorter range bands.
b.) It does not suffer in CC, as most other assault rifle do, due to its short length (hence its inaccuracy).
As per FAQ
Belzarach: CC: 0 DAM: 11
Invader: CC -4 DAM: 10
Now there's a major improvement in damage, making belzarach equipped units a threat in CC. A side effect, though...is that it completely discredits bayonets that increase damage from ST (ex. sectionner, Yari Shogun). Bayonets that increase CC become much more interesting by the same token.
I agree with you on these points. However, if you were to put a Sectioner Bayonet on a Kratach, suddenly, you have Legionnaires or - holy shnikeys! - Wheeled Templars running around doing 16 DM;
17 on a Charge![/b]
With the improvised weapon rule
Belzarach: CC:0 DAM: ST+2
Invader: CC:0 DAM: ST+2
Important note: the belzarach does not have an optional load out, so cannot mount a bayonet!
The rule is greatly beneficial to ranged troops with weapons that used to be crap at hitting in CC, and even more so if they can put a load out. Troops like the ashigaru and necromutants get the shaft, comparatively speaking.
The following models are equipped with the Belzarach:
Destroyers - (ST 7 and also has a Dispatcher blade - no need for Belzarach to be equipped with a bayonet; though, if it was, they Destroyer would be doing DM 12 in CC - the same as the Blade, and the Blade can Sweep.)
Necromutants - (ST 5 - they should avoid CC at all costs, but they have a chance to score damage if they do find themselves so embroiled.)
Necromutant Leader - (ST 5 and they're Zombie Masters - that what zombies are for, to handle the dirty work. Throw a few of them in front of you, and run the other way!

)
Necromutant Spotter - (ST 6 - just like regular Necromutants, but stronger!)
Undead Crewman - (ST 4 - He's a zombie. If he gets into CC, at least the Carronade can still fire on its own!)
Neronian Legionnaires - (ST 4 - what do you want; they're not-as-brainless zombies...)
Necrotyrants - (ST 4 - they're Unscrupulous. That won't do them any good if they're tied up in CC.)
Blessed Legionnaires - (see Zombies.)
Blight Commando/Sgt. - (ST 4 and all the goodness of Aura of Darkness; folks gotta pass a LD Test just to attack them in CC!)
I do not really see a play-balance problem here, but, I would not be averse to adding a Dark Legion Bayonet to the Belzarach, as the picture in the DL Armory shows. I will run that one by Thom to see what he has to say about it.
As for the Ashigaru, I believe that we took this into account, nicely. The weapon has a 1" reach, which means they don't even have to be in base-to-base contact to conduct CC, and can lend support to those who already are by virtue of that reach. Further, they were doing ST+6 prior to the "re-write" - a coincidental 10 DM (they're ST 4) - same as if they'd have fired their weapon.
With the "re-write," they are, still, doing DM 10. Worked out nicely.
To me, I would've been content to play by the FAQ. However, because of the confusion created by the rules, as written, it left open for interpretation exactly what an "ad hoc" weapon was.
Having been in the military, and having wielded a bayonet, I know that not only would I attempt to stick my enemy, but would be pulling the trigger the whole time. Yes, an M-16 makes a horrible spear, but, it is what it is. That said, to me, the entire reason that the CC modifiers are listed is because it is difficult (not impossible) to bring a weapon of size to bear in the furball that is hand-to-hand combat. Now, stick a Yari polearm on the end of that rifle, and see if it makes the job
easier.
So, Dodger came up with what I think is a great way to interpret ad hoc weaponry. It ain't official, and would not be used in a tournament - the FAQ would rule in a tourney.
If this still seems funky to you, please, try it, and report back.
Thanks.