Car going through a lot of alternators is usually bad quality replacement units or staying with a bad battery. Because of say a dead cell the alternator never gets a rest from charging. It's just trying to catch up but it just can never get there.
To get a grip on your situation I would wire a voltmeter into say the cigarette lighter socket. Watching what your meter does voltage wise over a couple of days is going to lead to some conclusions pretty fast I think. Or at least indicate where you have to look. There is something strange here.
If you can make that light glow with manipulation of the throttle while car is stationary just monitor the battery voltage. If it is say 13.5 volt for example. Rev the engine a little and watch your voltage. If it rises a little that is normal.
You will have to have a second person to inform you of any indicator light change. If the voltage also declines a little that is also meaningful. The problem with a leaky diode concept is usually the leakage would be constant. It possibly could be intermittent but not likely. This methology will start to zero you in on exactly where or what the actual problem is.
There is a good chance for example that the alternator is putting out properly yet the indicator circuit is intermitently malfunctioning. Prove that first. Could also be the alternator is not producing consistantly as well. Voltage monitoring should help a lot. Your suspicion that something is wrong in the wiring could be valid. I just had a look at a wiring diagram. I was not estatic by what I saw. But first eliminate the other possibilities. The indicator circuit does look a little more complex than what I thought it should.