Skillers, sapping sappers would be weird, you would here-

'Spy sappin' my sentry' then 'Spy sappin' ma sapper'

Mayhem....

But then could you sap a sapper thats sapping a sapper....?Yeh.....

An Engineer being able to move his stuff would be useful- sentry lv 1 would be slow, sentry lv 2 would be slower, sentry lv 3 would be extremely slow, dispenser same as lv 1 sentry, teleporter would be quite slow but faster than a sentry. A fellow Engineer could assist and double the moving speed as well (same way that a fellow engineer can help to build stuff).
A spanner could be an alternative weapon. Right trigger allows the Engineer to remain totally focused on his sentry unless right trigger is tapped again, then the engie will take 2 seconds (same as spy cloak) to take his spanner off the sentry- he will always be repairing it at an unbeatable rate, however he cannot turn around so an ubered pyro can get in close, kill him and then the sentry now that the Engineer isn't there. The spanner will swing slower to repair but repairs 100% of damage and is weaker than the wrench in combat.
A new contraption is a man-trap. Similar to Demoman stickies, these traps open up when the Engie clicks right trigger and will catch lots of people. Soldiers/Demomen can get out by rocket jumping. The enemies are stuck in there for 15 seconds, slowly losing health then killed unless someone else kills them beforehand. They can be noticed though by the floor looking slightly lower than normal floor.
Opinions?

Hawke, imagine having teleporters and dispensors walking arond
Someone would come and be like 'Where's ma dispensor, it was here earlier?!'

WAlking sentries would be like Droidekas from Star Wars.....awesome

Awesome but much more easily beatable... when the Engie is carrying his sentry, it takes him the same time for a Spy to uncloak/cloak to put it down again to start repairing it and he can't repair whilst he is carrying it... however a fellow Engineer can help out by repairing it but if he was helping to carry he takes half the time to let go of the Sentry to start repairing it... and the Engie can only carry his stuff, not anyone elses, he can only assist someone else carrying but can't himself move them...

Spy needs a cork...

Stuff it in the end of the enemies weapons so that the first few shots they try to fire fails and perhaps does some damage back to them...

Now that would be quite interesting. "Spy corkin' ma shotgun!" Would possibly be hard to impliment and, like backstabs, buggy.

Backstabs are still bugged... some people just can't be backstabbed... this has happened all the time to me.
*sneaks behind Heavy* *backstab initiated* *backstab lands in Heavy's back* *Heavy yells in pain* *backstab initiated* *backstab lands in Heavy's back* *Heavy turns around* *Knife slashes Heavy's face* *Sasha mows poor Spy down*
*walks plainly past Skillers cloaked* *uncloaks behind Skillers* *backstab initiated* *backstab lands in Skillers back* *Skillers yell of pain is muffled by his gas mask* *Skillers spins around and flames poor Spy*
*sneaks up on Wynney cloaked* *Wynney shoots at poor Skillers in distance* *Skillers dies from a headshot* *uncloaks whilst drawing knife* *Wynney is unaware and zoomed in on a Heavy pushing the cart* *backstab initiated* *backstab lands in Wynney's back* *Wynney ignores the minor stab* *Wynney kills the Heavy on the cart* *backstab initiated* *backstab lands in Wynney's back* *Wynney draws SMG* *Knife slashes Wynney's smug face* *SMG mows poor Spy down*
Those are real life examples that have happened in the past... rather buggy
Better yet would be an EMP glue substance that disables all weapons apart from melee weapons on a class for 10 seconds.

I'd like a shorter cloak time for the spy but you can recharge it with ammo packs,

Traps also sound like a good addition to the engie, but what would you take away from him for the abilit to place these traps?

Just have it replace a weapon, like the shotty.

4 new traps to replace his shotgun. He can surround himself with them.

nah, dont have the ability to make teleports but instead can setup say, 2-4 traps.

Sorry don't these traps sound like one of the original TF2 grenades that Valve changed their mind on?

sentry can only be built to level 1, but can shoot disguised spies. (cant shoot cloaked spies)

^ Overpowered totally

How would be able to get a sapper on it

That's actually underpowered, spy can circlestrafe it, and it's much easier to destroy as other classes (a level 1 sentry is easy for a pyro, 2 and 3 are hard).

its definately not overpowered.

I really think the cork would be cool, however annoying
BUT
hows this --> when your wep is corked, it fire the cork and does double damage for that shot

Not really... if you were the Spy, by corking the weapon you would probably be the death of one of your team mates if it does double damage...
A weapon that you would be able to use against other classes without it dropping your disguise would be useful though.. for example, the garotte suggested would do fine as you can kill without dropping your disguise. However it does make it obvious that a Spy is about since your team mate is grabbing his neck and choking on something whilst a supposed Pyro is running amongst the rest of your team and they start choking and grabbing their necks...

lol yeh
the advantage would be sentries couldnt kill you though
If that you could kill whilst invisible, that would be ridiculous though
tbh i dont care about spies

How about...
A Disguise kit that makes it so you can't be set on fire...but sentrys AND SNIPERS can see you. Maybe engys aswell...and don't say ' but it only shows knife ad revolver and that' I know...I'm just speculating

i would enjoy being able to see spies

will that is weird
why snipers?!
and if engies could see, whats the point?

A disguise kit that allows you to choose which weapon you appear to be carrying would be much better- Medics never use a Syringe Gun nowadays (Blutsauger maybe), Engineers are near buildings with a wrench (not a shotgun), Spies run around with disguises and a knife (not a revolver at most times).
A good cloak upgrade could be that when attacked, you won't show up but it will cost you a lot of cloak time (e.g. 10% every time you are hit by something) and you will be hurt as normal (flames won't burn you but like a Pyro you will still take contact damage). This will not negate the Pyro's ability to SPy-check as he can still negate a Spy's cloak by depleting it in a couple of seconds and generally Pyros pump enough flames into teammates to kill them anyway...

Having a cloak that makes spies fireproof adds another way to get rid of fire, which won't work.

Technically it doesn't make them fire-proof, it just makes them able to withstand the flames a little longer before showing up. But I see your point.
Metritutus? Your opinions and suggestions on Spy updates?

snipers get aimbots but also a VAC ban ;o