I think no-scopes are fine the way they are; the shot's enough to put down an injured pyro charging you but not enough to abuse with a transparent crosshair sticker (Quite easy to get). Faster charging time would be awesome on a sniper rifle, but something like a complicated bolt-action that takes longer to fiddle with between shots would balance it out more; on a number of maps a smaller scope wouldn't do much. Usually there's 2-3 spots an enemy sniper could be, and you can't see each one at the same time from all the spots, or they're sufficiently close to the edge that your eyes won't pick up the movement. You're still gonna get blindsighted with the normal scope, a shrinking one won't really cause all that much difference.
Anyways, I have a few in mind for Spy.
New cloak watch- Replacable, but less durable batteries.
+Ammo crates and fallen weapons recharge cloak (possibly by set amount, like the tiny crates give less, etc)
+Shift fully into cloak faster
-Cloak lasts 75% as long.
I'd see that as fairly balanced; allows you to go into cloak more often but not for nearly as long. To actually get behind enemy lines with that watch on maps like Dustbowl would require a bit more espionage skill, to get closer in disguise without actually getting spotted, but would allow you to sap something, grab a crate or steal ammo from a dispenser, and immediately cloak out.
New sapper- Sabotage Sapper.
+Does permanant damage to buildings; e.g. blocks the HP of buildings from going back up past a specific point.
-Does significantly less damage to the building, -50% or so.
This one's definately slated towards either progressively working down a sentry that multiple engineers are covering, or weakening one to the point another member of your team can destroy it without much problem. Still works absolutely fine if you stab-and-sap the engineer, if there's no one around to fix it. (And if not, by the time they get over there it'll be sufficiently weakened)
Only two I have at the moment, but I'm still coming up with more ideas. I try to slate mine to have a use for the original version; kinda like the backburner, flaregun, natascha, and the KK. There's still reasons to switch back and forth between the originals and their updates, dependant on the situation and your personal playstyle.