As my group tested the weapons over the past 5 ranks we have like the infiltration of some characteristic based scaling, but we want more.
By making more weapons and powers scale with more characteristics you can preserve interesting or signature equipment's viability through the ranks and you can make the PCs relevance more driven by who they are than by how snazzy their flashy dakka has gotten.
Wargear should definitely get its pride of place in 40k, I agree, but I would love to see high end play still see some autopistols rather than be one continuous orgy of plasma/melta/power/cannon. This is especially true for signature weapons with a history or story, or even just plain appropriate for a tradition-bound setting.
Yes, subtlety and stealth, but that alone is not the answer.
The beginnings of a truly varied scaling system seem to have been implemented by the DH2 Armoury and I feel that going all the way is needed.
Some weapons scale RoA with WS. Fine. Some with AB. Cool. Some scale Pen, nifty.
Do more.
Make all weapons and especially all psychic powers scale in one or preferably two ways with different characteristics .
Perhaps all SP weapons have 1/2Pb pen with Sniper rifles being differentiated by the higher Pb Pen and the other special qualities it has.
All Las overcharge might be 1/2Ib rather than a flat number.
In the case of psychic powers, there is a great deal of potential for scaling.
Make Biomancy scale range with PL if you want, but have the damage or the Pen scale with Tb rather than PL. This forces psykers to diversify, eliminates stacking of a few stats, and can easily be controlled by doing things like TB-3 or 1/2TB as needed.
Divination frequently has Perception prerequisites, but I would really like to see it results broadly scale with Perception.
Telepathy could sclae with intelligence in a number of cases. I am not even suggesting that each be dependent on the characteristic, make WP tests still be the Focus power test and PL the primary means for scaling, but bring the other characteristic in differentiates specialized psykers and diversifies characters. Further it allows scaling without opening the system too much to exploitative stat-stacking.
I feel like the beginnings of the system I saw with the first updates where high agility characters might use whips and daggers and high strength characters might prefer power fists in melee could be expanded upon to give similar flavour and dynamic choice to both ranged weapon selection and psykers.