Free user space for non-graphics drivers

>I'm not sure how that compares from a security perspective to loading a dozen /lib/firmwares

That depends what is done with the stuff loaded from lib/firmware.

Normally it will be loaded onto some other device so the risk depends on the level of hardware access that device has to memory and the degree to which Linux can restrict it (by an IOMMU for example).

So for example firmware loaded into an I2C connected touchscreen controller is unlikely to be able to do much harm since that bus provides no DMA capacity, worst case it could simulate clicks to enter false data (assuming it knows what is on the screen).

On the other hand firmare for hardware with bus mastering DMA capabilities not restricted by an IOMMU basically has full system access.