Digi probably should have been written as S-2 all along - it's a complete outlier as far as close combat weapons go.
The other weapons (at least in the old Comprehensive rules list thats the closest to hand) that have specified strength levels are: Las Cutter (9); Web Gauntlet (3); and Xenarch Death Arc (3).
Las Cutter is a Lascannon as a blowtorch. Web Gauntlet is silly string on a glove. Xenarch Death-Arch is an electrical zapper.
A great many Van Saar fighters are modelled with cables leading out of their central nervous system - it's entirely conceivable that their digi-weapons are wired into the circuitry of the cyberteknika.
Digi weapons have melee and versatile traits, both are triggers for the gamma level benefit (unless the either/or wording somehow cancellation this double-up of eligibility, which seems weird).
As mentioned, the fighter most likely to get the benefit is restricted to 0-3 of the digis, for a cost of 40 credits (tek) plus 75 (digis)
The list of other weapons you list and the Digi laser (which as well as the Digi multi laser from that Necromunda Apocrypha Blood in the Spire in Warhammer Community) are all the Melee and Versatile weapons that are
not keyed to a fighters Strength. ( I think they are it at least)
They all have one thing in common. They are basically all guns of some sort
A mini las pistol, a Lascannon blowtorch thing and so on (love the silly string
). It will not matter how hard you swing them you will not make the laser bolt or space electric arc go faster or burn hotter, the silly strings real effects are in the sedatives and throwing string harder does nothing.
They are more like using a side arm in close combat than a club. You don't add your fighters strength to a las pistol or a plasma pistol shot in melee do you?
The Gamma and Omega benefits are applied to the fighters Strength characteristic
not the fighters weapon. That's what the rule says. If it said fighters weapons or the fighters strikes that would be different. The Digi laser, and the others you and I have mentioned, do not involve the fighters personal Strength Characteristic at all so the Gamma and Omega cybernetics benefit does not apply.
The Versatile trait requirement in that cyberteknika is actually redundant given that it has all Melee trait weapons as well. All Versatile weapons have the Melee trait so why bother putting Versatile in as well? That's GW weird "editing" for you
By keying it to the Melee trait it does lock it out from the pistols with the Sidearm trait as they don't have Melee so you can't use the cyberteknika to boost your plasma pistol.
Your Archeotek only has a 0-3 limit on its starting equipment list, say your founding gang or when you use a normal trade action to buy equipment for your Archeotek. You can still visit the Trade Post and use the Seek rare equipment option to buy more if you want to go full Beware My Laser Fingers Mwahaha!
Or just get a Laser Cannon.
