Why are there no decent 9V block chargers?
I can mostly answer your Q2:
the reason you have


  yet not seen a charger that displays the current charge status &amp; progress bar and has a reliable charge stop.


is because 9V-rechargeables are a very niche product, which also has a lot of fragmentation:


6 NiMH cells (require charging to about 9V, nominal average voltage 7.2V)
7 NiMH cells (the most common I've seen, require charging to 10.5V, nominal voltage 8.4V)
8 NiMH cells (require charging to about 12V, nominal voltage 9.6V)
2 Li-Ion cells (require charging to 8.4V, nominal voltage 7.4V)


So typically the manufacturer of the battery would issue some cheap charger with it, and warn in big letters that you should not try to charge other brands (I've had a Tronic (LIDL) one, which even had percentage indication IIRC, but all other ones I have are noname cost-cut trickle-charging ones, which ruin incompatible batteries very quickly; you get what you pay for, i.e. almost nothing).

The other important reason it is such a niche product is because of their very small capacity:


A typical primary 9V is ~600 mAh (with alkaline cells), while a typical NiMH 8.4V rechargeable is just shy more than 250 mAh.
Compare with AA and AAA where the rechargeable versions nearly reach the capacity of their alkaline counterparts.


On your question 1, I don't know for sure, but I suspect the fragmentation alone makes the detection almost impossible. Compare a 1-cell NiMH vs 1-cell Li-Ion - the detection is a piece of cake, just a voltage comparison. For the 9V the voltage ranges overlap, so you may try to do some sort of internal-resistance detection trickery, yet I suspect that would be quite unreliable. In the end it would probably be best just to avoid mixing charger/battery manufacturers for the sake of safety¹, and we arrive at the status quo.


¹ yes, unprotected Li-Ion 9V block could definitely explode if charged on a 8.4 NiMH charger. OTOH I've only seen protected Li-Ion 9Vs but I have not dared to test that part.