I be damned
found another option...
The BJT is lacking the intrinsic diode thus blocking current both ways, and those most modern late PNP BJT are quite on par with those recent MOSFET switches!
enter:
2SAR552PIt can be driven off 30mA pins, can drive up to 3A pulses (way over USB supply) all in all a simpler switch, and if anything odd where to happen i have the fly back diode in place on the base (brought to bear should reverse current ever flow over the device)
Why this exotic PNP/PMOS layout you may wonder?
Earlier I have decided to have all the backlit LEDs connected to common ground to make the PCB layout simpler, this mandates so called high side switching, and as far as i am aware this is most reliably achieved with BJT.
This is so due to BJT being current controlled devices that only slightly depend to discrete voltage levels - which are a moving target in said high side switching.
Further a note on the dreaded BJT thermal runaway (losing resistance under load and when heating up):
If a single device is used this is totally no issue - it loses resistance as it heats up - thus heating up less - that's about all
It remains only to find out the proper amount of
milimaps required per LED to achieve the needed level for a backlit key effect.
This is the more difficult as we actually try make a board for more than just one color of LEDs (white, blue, amber, maybe more)
Am i overthinking this?