Ok, so here are some suggestions(some of them were suggested be4):

The knife
I think this little beauty should pierce through people, like a barrett bullet.It would be cool I think.

Aero dynamics
Well, dodging is pretty much luck nowadays: I say you should fall slower (much slower) when in prone, and there should be some kind of method to make you fall faster.Parachute should also be shootable.

The grenade
-I believe there should be a setable fuse like 1-3.The keys should be bindable to anything, for utter customization.You could set the fuse anytime, and it would stay on that setting until you change it.
-Grenades should explode upon impact with soldats maybe.
-The nice explosion animation is just eye candy: I think while you see the fire, you should be set on fire when you walk in it.

Boost
Discussed a lot of times, but I wan't to force it: double tap a direction and by consuming jet fuel you are boosted about half a screen.There should be a 5 seconds cooldown, so it won't be abused like hell.

Not bad, but most have been already suggested. I guess you are making these known. Best:- Aerodynamics

I like everythigjn besides the boost and this -Grenades should explode upon impact with soldats maybe. - Nades already blow up on impact, well usually it does.

Yeah there should be some method to dodge bullets while in air(the proning doesn't always work :( )

1) THe knife doesn't need to go through people..it's not nearly as powerful as the barret, even if a one hit kill is possible.
2)While the chute should be shootable, you fall just as quickly when you're prone as when you're standing...makes no sense to make it so much different for soldat.
3)Been discussed...no...too tired for helpful criticism, sorry.
4)Interesting, but people already have enough methods for boosting themselves (i.e. nades, m79, minigun..)

1) Yes.
2) No.
3) No... but hey... in my 1.1.5 version grenades explodes on soldier impacts!
4) NOOOOOOOOO

5 seconds cool down on the boost? that would get abused as hell anyway.

I agree with all of these.. 'cept the boost. As for the knife going through someone.. once it's killed 1 person, then it shouldn't be able to kill someone standing behind that person too.. Maybe it should just slightely injure them.

1-4) No.

If anything, knife should be reset to 1.1.5. That aero-dynamics idea... lets not go there. With the grenades, why ruin the simplicity of Soldat? And lastly, boost... it doesn't feel like Soldat's style for some reason... and yet again, it would ruin the simplicity.

the only thing worth mentioning was the aero dynamics, but why complicate soldat?

i noe
soldat is already good as it is
ull have to learn not to expect too much from the game