Fix what? it's not broken.

What exactly are you expecting?

You appear to be under the impression that doing an emergency blow should be some regular operation. As people have said: it's not. It's not just the reverse of a crash dive or something.. this is basically an "abandon ship" kind of move. If you're lucky, it'll give you the chance to make enough field repairs to get you back to base for a full repair, but you shouldn't be doing it unless you're basically acknowledging your patrol is done for.

What must they fix, there is nothing wrong with the game. When you blow ballast you use all your compressed air to blast out the water in your ballast tanks and when your on the surface you need to fill your compressed air tanks with air because they are empty. There is no such thing as fill it up with just enough water to dive because once you let water in and your weight is greater then your displacement you will start to dive but if you compressed air tanks are empty you will continue to dive until you pass crush depth and implode. If you have air in your compressed air tanks then you can once you dive use the air to push some water out so that your weight is equal to your displacement so you can hover but if you don't have any air in your compressed air tanks you will continue to dive because you can't force the water out.

This might work but will make so much noise that you might as well just blast stereo music because it will probably be just as loud.

I'm never using the Blow Tanks feature, I just set the ballasts and planes to maximum, this has the same result without the big sound spread around.
I would use it if my sub is too damaged with propulsion and planes not working, then you don't have much other choice or you will soon implode when going down...Be aware that once your hull is damaged, your max. depth is greatly reduced, the game is far too generous with that 'death threshold' IMO. With 30% Hull I still was able to hit the 800 feet depth safely which is not realistic. With more realism you would indeed use the Blow Tanks more frequently.

I don't see (or understand your point) that while playing these emergency tanks don't work as intended, and 2 minutes waiting time for resetting the needed pressure are really generous compared to the real thing. In the game, these 2 minutes are however an 'eternal' time to wait, unfortunately AFAIK you cannot mod it; in this time you are completly at the mercy of surface enemies and planes.

:/\\!!:/\\!!:/\\!!

I must say, Bingo_Pete, these guys are dead on in their responses. For a playable realistic submarine simulation video game, this game strikes a near perfect balance. Nothing is broken. There is no bug nor a glitch. As aggravating as it is to you, what you are requesting, demanding, is the equivalent of a "Wait, wait, I have to reload," when playing a shooter game in which you made a bad tactical error.

I, along with many here, have blown ballast for one reason or another while playing this game -- usually with full rise on the planes and at flank speed. Usually it works. Usually. However, I know it's a gamble as I'm going straight to the top for a time. I also know I made tactically unsound decisions when that happens. Just a game. Learn from your error and move on.

yeah, despite how it always appears in movies, Emergency Blow is not really a good tactic for torpedo evasion, it should leave you vulnerable on the surface.

It should be noted that you can drive yourself back under on the planes, you just can't use the automatic depth controls to do it. Ring flank speed and full down on the planes, you'll sink like a rock.

American SSN's do not use AIR to change the buoyancy (weight) of the ship. Using air is NOISY evolution in most circumstances and that's why is it not normally used. In the real world, after an EMBT blow and you wanted to re-submerge, you would just open the main ballast tank vents.

If a sub were to dive in this state (i.e. opening the vents to re-flood the tanks after the blow before recharging the compressed air tank) wouldn't that still be quite dangerous since the emergency blow system would be inoperative (little to no air) along with the torpedo tubes (assuming we're not talking about swim-out weapons)?

You are confusing peace time operational procedures with war time realities.

US Submarines do not use the EMBT blow system to routinely surface the ship. They drive to the surface and start the Low Pressure (LP) blower to blow the water out of the ballast tanks.
So, if in a war time scenario, you actuated the EMBT blow system, got the casualty under control, you can now re-submerge and start an air charge. You most likely will not 'blow until equalized'. You are going to have some air left in the tanks. Plus, unless absolutely necessary, you are not going to go back into battle.

You can also do the blow, decide that you do not need to surface and vent (open the MBT vents) on the way up.

With the air charge going, you are drawing air from the 'people tank' and when necessary, go to Periscope Depth (PD), raise the snorkel mast and 'equalize ship pressure', bringing vacuum down and putting a small pressure in the ship, and go deep again. We do this all the time.

You CANNOT pull air from the ballast tanks.

it would be nice if the ships had a snorkel in game, for just that kind of event. Also, the ability to partial blow the MBT would be useful.

Useful how?

Very useful during some operations.

Surfacing through the ice.
Jump 50

and so on...

The 637 class had a normal blow system which blew the MBT's from air bank five only.

During normal evolutions sure, but we're not surfacing at the North Pole here. How would it be useful in a tactical situation?

In the approach to a target, not very useful.
But in some scenarios trying to infiltrate someplace, a Jump50 would save you from grounding and damaging your ship. You are just risking an air transient.

In the game, not very useful...