One frustration I have with Cura is that it has no way to set print speed in terms of a volumetric extrusion rate, when extrusion rate is the main physical limiting factor for how fast you can print. It's a pain having to have different speed profiles for different layer heights (and doesn't work with adaptive layers!), different line widths, different materials, etc. I'd like to just set a feedrate limit on the extruder axis, which would achieve this and make it easy to switch already-sliced models between different materials. However, having a low extruder feedrate limit would make retraction and recovery from retraction incredibly slow, to the point of being unusable - since I've found quality so much better without combing, I now have a lot of retractions.
I'm thinking about building Marlin with support for firmware retraction in hopes that the firmware-retract command can ignore the configured extruder feedrate limit to still do rapid retract/restore, but I don't want to waste a lot of time on it if that doesn't work. Can anyone with experience with this feature confirm whether it ignores the normal extruder feedrate limit? Or, if you have experience with a similar configuration, can you share results on how well it worked?