The hesitation in your post just shows that you arent sure.

Also, half of the suggestions you make are unreasonable, as it will make a decent unit to a totally useless unit or changes the race's intended design.

Siege Tanks are fine the way they are.

I think the problem lies on Zerg themselves, as there are claims saying that they are lack one unit, like a Lurker. Or maybe just buff Roaches back. I just hope Zerg doesnt have that fundamental problem which is hard to fix. Something like DoW's Tau or Tyranids where they either can be too strong or too weak.

Im Protoss player,hence, i have nothing to say on the balance of the game.

If there are more than 1 or 2 BC and there is no counter, something is wrong with you, not overall Terran balance.
I think it's more like Zerg isnt very well designed in the first place.

Im still not a fan of Hydra can only build after Lair.

don underestimate high templar, MMM ball can be smashed like taufu if u know how to use it... if u know how to... IF....

btw , terran pwn u too much isn't ? y feel so offended ? lol.....

to me, zerg has sort of become Scrin.

colossus is like the Scrin tripod.

Starcraft 2 all those units have their own weakness. It's ok to me.

I just don't like one.. i can use 1 Viking to kill few Battlecruiser (without yamato) with proper macro hit and run. BC need to add range!!!  how come expensive unit with big gun but with short range.