Experts
With experts like this who needs conspiracy theorists.
Yes they will activate on contact with water, if not malfunctioning. But no they don't transmit very well from under water, Something about electromagnetic waves and mediums. Hence you have an acoustic beacon.
Search areas.
From altitude by the time they hit the floor, can give a large search area. Just reinforces how hard it can be to sea search, especially if the weather is sh!t. Depending on impact pattern and type of break up, it may not be conducive to finding.
Satellites and real time.
We can go for the rolls royce system or basic reporting position system.
Yes almost every thing is possible with money. But to what end and what purpose? Most resources goes into prevention. We already have an onboard system that these days can tell almost as much as you want.
Most of what your asking for is not prevention, its convenience, in the odd case of never finding the BB such as MH370 or their damaged, yes real time would be the go. But that requires money.
In this case they think they know where it is, and still can't find it yet, I don't think a real time position report would help if that was the case. If it turns out it is significantly away from where they think it is, then yes it may do.
Communications
Aviate, navigate Communicate.
As my old flying instructor used to say, Fly the F#$% airplane first, instead of trying flap ones trap. If things turned to Sh!t, they may be too busy trying to save themselves and every one else's @rse to boldly announce to the world they are going down.