SSD
Sure, a speed at which an aeroplane at a given loading (G and weight) will stall can be calculated if you have all the data, which you don't.
What other data do you want for a light aircraft, the calculated stall speed is given for most light aircraft at max weight, in unaccelerated flight 1g, in a given configuration, clean and with flaps extended, those are the bench marks.
Below max weight then you will have to go out and experiment to find out what the stall speed is at lower weights but to be honest why bother on a small aircraft when there is probably only a few knots difference, thereafter you can times it by 1.3 for an approx. approach speed.
An AoA indicator gives an unequivocal direct simple read-out of how close to the stalling angle you are.
When you have an AoA fitted to your chippy and you are side slipping in to that grass strip tell me if your above statement is true.
The majority of light aircraft stall spin accidents in the circuit happen around the turn on to base leg and final approach or short finals, generally when the workload is high for the low time or out of currency pilot. The reason, because they were not monitoring the airspeed, i.e not looking at the ASI or due to workload not registering what it was telling them.
So lets add another gauge AoA for the same pilot, do you really think this is now going to get anymore attention in the same situation ? an AoA is nothing new they have been around for years since the Navy developed them for carrier landings but unless the pilot has the ability to actually fly and monitor the situation developing around him/her then no amount of instruments are going to help.