There are multiple variations of weapons, so anything with a combat purpose must have 'some' stats. Behaviour were looking at a number of ways to handle this, and their preferred route for quite a while was unique stat items being in the RTS. In the face of fans raising the issue that this was going to create a lot of suspicion, and bore the risk of P2W (sod's law says at least one variation behind the paywall will be considered OP by players at some stage, and will then be held up as proof that the entire concept was all about P2W. *sighs*), Behaviour indicated that they'd look into allowing RTP to be earnable - from the outset, they've been absolutely clear they dislike P2W mechanics, and aren't trying to introduce it via the back door. This latest clarification from Miguel in the newsletter goes one step further - actually going back to the original monetisation mechanic proposed, which was that the RTS would be purely cosmetic variations of existing in-game items. A lot of people will be pleased at this - Grig in particular, as he's been arguing for it ever since Behaviour's analysis suggested it might be financially unworkable and wanted to explore alternatives. As Grig's OP points out, this says a heck of a lot about the ethos at Behaviour when it comes to listening to the community.
While I completely agree and support the idea that all RT items should be cosmetic, I actually got the Heresy Pack (Now Dawn of the Imperium) because of the Phobos Pattern Bolter. In that, I hope we will have different Bolter patterns to choose from (A harder hitting, slower RoF pattern), and apply this "cosmetic" to.
I personally hope that the cosmetic items are for a specific loadout of the regular weapon that is "gilded" into a cohesive model. So if you take a stalker bolter and add a special long range scope and target tracker, you can skin it to be the legendary "Nightscope" bolter of some Behemoth campaign that has the scope and tracker built into the appearance along with some tassels and checkmarks for killed carnifexes or whatever. Or if you take a shoota and add a combi-burna and a choppa end, you can apply the skin to make it into the "Sqiggler" that shoots a stream of corrosive pulpified squig out the end instead of fire. Same stats, obviously, but basically it takes a weapon with specific attachments built for a specialty purpose and makes them look like the've been designed into the weapon rather than just added on. I think that could be really popular, since people love settling into their roles and custom loadouts, and this would be a cool way of legitimizing the ones they choose or suggesting new ones.