Sapper maybe?
they'll never replace the sapper, it's as central to the spy as the disguise kit.
Honestly, if you used the Dead Ringer (assuming no disguise kit) with either the regular watch, or the Cloak and Dagger, it is very possible that you could stealth around their base invisible near constantly, and if they find you, you can appear to die and escape. It's just as effective, if not moreso, than the disguise kit. It is, in essence, a second type of disguise.
edit: you'd still be easily found by routine spychecks. This spy is also very offensive, and lacks the capability to sap (mostly) due to lack of disguises. It essentially would make this type of spy into an assassin, and less of a utility character.
Instead of an impersonation spy, you could be an infiltration spy. Different play styles for different people.
Also, are the released Sniper updates actually real? Like the Bow and Arrow, that's really cool.
yes, it's been confirmed to be a dual update.