What prompted bringing it up again in the first (err, nth) place was the techmites.
For normal fighters, the cost of a PP weapon factors in - presumably? - the bonus nature of them. If you've a ganger with multiple attacks and you're fancying something like a power hammer, your choices might include the Power Hammer and the Gem Cutter, similar profiles and similar costs.
But that similarity evaporates if you can only make one (bonus) attack with that 50cr weapon.
So look at the techmite. They've 1A. But only get PP weapons. How many attacks does a techmite with Bolt Spitter get in melee? 1 unarmed + 1 Bolt Spitter? (If like Digi, yes?) On the charge, 2 unarmed + 1 Bolt Spitter?
My sense of it - which may be wrong - was that they're still viable weapons. If you've a 3A powerhouse of a Leader with PP melee weapon? They could make 4 attacks, if they've another weapon (even if Unwieldy!) as well, or 3 attacks with the PP weapon if its their only one.
Obviously the limitation is also there for sidearms: extra attacks don't benefit siderarms much, but you can make the extra attack with one, right?
So take a techmite autoveryor, with Bolt Spitter and Arc Welder (for a cheap & smooth 200cr), on the charge it'd have...
4 attacks: 1,+1 charge, + Arc Welder, +1Bolt Spitter
Or
3: (1+1) Arc Welder attacks, +1 Bolt Spitter
Either way, 200cr for the situation makes very little sense, but that's sorta neither here nor there.
But I think the "3 attacks" feels like the intended outcome where techmites are concerned.
So for a Charter Master w/Arc Welder & Stub Gun, you could plausibly be making... 3 Arc Welder attacks on the charge, and +1 from the stub gun?
(But not 3 for a Stone Burner: that's limited by Sidearm.)
Which reminds me, the wording still doesn't support four-Sidearmed squat gunslingers, does it? Twin Guns Blazing is very much *two* guns, even if you can reasonably shoot four of them.
(But in melee... It'd be only 170cr for two Stone Burners and two Ironhead dum-dum stub guns!)