This psu design is good, not perfect, many companies use switched xformer secondaries to limit thermal dissipation at low voltage output ,,, you have some models with 5 secondaries taps ...
The lm 723 design(s) are proven, you can add some trick(s) to get it down to zero volts etc .... this psu as a floating supply design for the regulation section, it give better stability.
You could help the cooling with an temperature controlled fan on top of the heatsink, or add an small temperature controlled fan driver board ...