Simscape has some nice thermal domain elements like Cauer thermal model elements.
I can think of how to do this manually. You input a pulse and measure the power of the pulse, and you look at the temp rise associated with that pulse. dT/dP gives you the point for that pulse duration. I think for pulse trains / duty cycle you do the same thing, but you wait for temp equilibrium to establish dT/dP.
What I'm not sure how to do with Simscape is run a plot that automatically sweeps all of the above.
but I'm not sure how one would extend it to Simscape / graphical interface.