Shadowsun's Stealth Cadre: "This card may enter play as an attachment with the text, 'Attach to a non-Vehicle army unit. Attached unit gets +2 ATK and +2 HP.'"
So, contrary to your comment above, there is no text saying that you can deploy the Cadre as an attachment - only that it may enter play as an attachment. So if deploying a Deep Strike card means that the card has all of its printed characteristics until it actually enters play in reserve (and they are preempted), wouldn't that mean that the Cadre also has all of its printed characteristics until it enters play as an attachment (and its "unit" characteristics are preempted by its "attachment" characteristics)?
Said another way, if I am understanding your reasoning correctly, a Deep Strike card is deployed as whatever it us right up until the moment the deployment is successful and the card actually enters play in reserve. And as such, the card is subject to all restrictions on deploying whatever it is (such as the Enslavement Dial) right up until the deployment is successful and the card actually enters play in reserve.
If this were true, then the wording on the Cadre should follow the same logic - it is deployed as a unit right up until the moment the deployment is successful and the card enters play as an attachment (because its text does not say it can be "deployed" as an attachment - only that it can enter play as an attachment). But we know that's not how it works because the Combat Action on Ambush Platform ("Combat Action: Exhaust this support to deploy an attachment from your hand.") can be used to deploy the Cadre as an attachment - despite its text only allowing it to enter play as an attachment.
This indicates that once you announce your intention to have the Cadre enter play as an attachment, the restrictions for deploying an attachment are applied, NOT the restrictions for deploying a unit -- which then enters play as an attachment. Doesn't it follow that once you announce your intention to deploy a card into reserve, the restrictions for deploying a card without characteristics into reserve are applied, NOT the restrictions for deploying whatever the card's printed characteristics are -- which then enters play as a card in reserve without characteristics?
Further, if the restrictions for a "face up" side of the Deep Strike card are applied while deploying the card into reserve, how could a Deep Strike event ever be deployed into reserve, since events cannot be deployed by definition? Doesn't this pretty decisively indicate that deploying a card into reserve does not consider the characteristics of the face-up card during its deployment?
Again Your comparison is not apt since one the text on both the Shadowsun Stealth Cadre and Gun drones specifies when its state changes to the moment it is being Deployed or Entering Play, your argument is that Deep Strike rules do the same is an assumption without rulings to support it. The fact that Deep Striking cards even go further to specify that interrupt effects to modify the cost of deploying such cards cannot be used further strengthens that position since if those cards had no characteristics what cards could modify them to begin with? Deep Strike rules further specify that Deep strike event cards can only be played from Deep strike reserve. and as Necrons do not include event cards from other factions its not really a consideration anyhow as far as the enslavemet dial is concerned.
I saw no FAQ or rules to support your position about an Ambush Platform allowing you to deploy a Shadowsun Stealth Cadre, perhaps you can link those or are those unofficial rulings not posted to the games FAQ? Or are you referring to the entry about Gun Drones?
Or are you simply trying to say all Deep strike cards inherently have the constant effect of having no characteristics simply because they are Deep strike cards? I think that's a far stretch to take.