Best practices for parallel DC/DC Boost Converters
Is this a reasonable approach?

Yes and personally, I'd just make several boost circuits like this: -

And have one controller that cycles through each MOSFET producing the right level of duty cycle to transfer (using DCM) the correct energy to deliver 27 volts for the 10 Ω load: -

It looks like all three are in parallel but it's down to how you alternate each one in terms of the control inputs CA, CB and CC. All three are sharing the power losses when driving the load.
So, where you and I probably differ is in the implementation; you are trying to use multiple controllers whereas I'm favouring one controller and some sequencing logic to drive individual boost circuits.