Your new circuit will not work because the added transistor turns off when the output voltage is less than about 27.5V. Also the voltage-setting pot turns down the amount of negative feedback when its voltage is turned down.
I made an extremely simple opamp with 3 of the transistors of an LM358 opamp. It has a non-inverting input for your adjustable reference voltage (a pot from the 27V zener diode) and it has an inverting input for negative feedback from the output. Its inputs should work all the way down to ground.
Can you calculate its resistor values?