I want to do it the current way. That is, feed a gate of MOSFET with known current rather than known voltage. I also want to experiment with positive vs negative voltages.

So, I'm building a brand new "experimentorture" circuit! It is going to feature a precision automated gate threshold voltage measurement, potentially with datalogging.

The problem is, I'm out of relays that my signal gen can drive. But, I recalled I bought a photovoltaic optocoulper thingy VO1263 quite some while ago, and it is a perfect opportunity to try it out. It allows me to connect a mosfet (or a pair) to create a solid state relay. And it has two channels! Now I can short tortured transistor's drain to source during torture. I expect that to have a little bit of an effect on the quality of the resulting hacked transistor.

I don't dismantle the old blink torture circuit yet, it will come in handy for measuring transfer characteristics.

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I also wonder, what will happen if I torture a p-channel mosfet. I would bet, in contrast to n-channel, its gate threshold voltage will increase in magnitude. That is, the biasing will go the same way exactly like it does for n-channel ones. So, I think I will not be able to drive a p-channel mosfet into depletion. Only one way to find out...