Which of your rulesets would be best to use to run a skirmish campaign in the 40k universe: the idea is that each player would have a small group representing a rogue trader, inquisitor, or similarly powerful individual and their retinue. Kind of like Frostgrave in the Grim Darkness of the 41st Millenium.
Games might include a vehicle or two per side, and solo playability (for Tyranid-infested space hulks and chaos demons for warp incursions) would be a bonus.
Some games might also see player retinues banding together to fight a larger force controlled by the GM (+-40 models on the OPFOR).
Rules for psychic powers would be an added bonus.
In terms of granularity: a lasgun is not a boltgun, and a flak jacket is not power armour, so I would like these differences reflected in the rules.
Those are brave men knocking at our door. Let's go kill them!
Clash on the Fringe is specifically written as a Rogue Trader replacement:
You can level up characters, there’s a bunch of pre-made races (which map to 40K analogies without too much trouble), psionics (though a lot more subdued) and you can play platoon+ games without breaking anything.
An okay weapon selection and the formula is included so you can “roll your own” if you need to.
Nordic Weasel Games