gated-oscillator pfm
i like this idea, but it is not quite pfm. it is closer to hysteretic mode, which is a little more difficult to avoid the finer problems.
you may consider gated-oscillator pfm at first. you would use a simple comparator to compare FB to VREF. If FB is lower than VREF, logic high from comparator is AND-ed with an oscillator to give pulses to the switch. Once FB is satisfied, input to AND goes low and device gives no more pulses. In steady-state, device hops into pulsing at a rate dependent upon load.
This is simplest implementation, I think you should start out with this. But feel free to PM me if you have bigger dreams.