Not to my knowledge.

Could have missed one or two though, but I doubt it.

I’m considering an improvement for new modules that could cause issues with modules with odd output stages like this (no protection resistor + no bandwidth control).

yes and thus it also limits bandwidth.

I’ve read that befaco recommend to remove the protection resistor for their slew module (there were complaints about tuning issues when using it for pitch CV).

What problem is to be expected on downstream modules?

The protection resistor limits the amount of current the op-amp can be asked to source/sink. This can prevent the op-amp from being destroyed if, by accident, two outputs are connected together.

There are two configurations for the output resistor: one that causes slight voltage drops and results in pitch inaccuracies (used for most of my modules which are unlikely to process pitch CVs), and a more sophisticated one that does not cause voltage drops (which I use in modules generating/processing pitch CVs like Yarns). The configuration that causes pitch inaccuracies has a slight positive side-effect, though: it allows passive summing of outputs.

Bypassing the protection resistor has two negative side effects:

• More risks of damaging the op-amp through incorrect patching or ESD, since the output pin is directly “visible” from the outside world.
• If the circuit surrounding the op-amp does not attenuate high frequencies (for example, for example, in an inverting amplifier, no additional capacitor between V- and Vo), you can get ugly ringing and self-oscillation when long lengths of cables are patched to the output and/or when you connect the output to modules that have additional filtering or ESD protection on their inputs.

I have an older design VCO from nonlinearcircuits that produced a pitch change when the pulse width was changed (if I remember correctly). This is a design that has been around for a long time. Removing the input resistors was the fix for the issue.