Understood. I'm no engineer, but I believe the concern of water removal would be for the stability of the shell itself. When our FB pools are "set" and filled, they in-turn become "pressed" into the earth and expand a bit from the tremendous pressure. That pressure helps to keep that seal with the shell and ground. The concern with water removal is that that downward and sideward pressure is relieved, which may allow the shell to contract a bit, thereby breaking that pressure-tight seal against the ground. So the shell may tilt, shift, rise, etc. Would that damage the pool? Maybe, although your shell already appears to be damaged, so you may look at it as a last-ditched effort to save it. Also something to be aware of is your existing coping. If you have a cement patio, ledge, coping, etc around the pool, that reactive pressure could damage those areas as well - not to mention plumbing if the shifting was excessive.
So it's really an unknown thing for us. You may be able to make a more educated guess based on local authorities and information gained from your county or pool experts. Not an ideal situation by any means, but based on local conditions and current water tables, you may get fortunate and save it. I certainly hope you do.
Hey - Last ditch thought ....... just like with plaster pools that are drained, sometimes they drilled weeping holes to relieve pressure and allow moisture from a high water table to escape. If you have your pool emptied to fix a crack, you or your contractor "may" want to consider that same thing. Again, I'm speaking outside of my area of expertise, but it doesn't seem too unreasonable. They have to fix a long crack anyways, what's 2-4 weeping holes while they're at it to help keep the pool in-place? Well, the experts in your area can let you know if that's even a good possibility. Just had to toss it out there.