Voltage regulator 78L05 only provides around 100mA, but that should be more than enough for this job, and they're cheap and tiny.
Nice tip!
Next suggestion: instead of toggle or rotary switches, how about 2 momentary push switches with built-in LED illuminators? You could wire the illuminators to the same output pins that are driving the 2 FETs, so the pilot can see at a glance what the status of the exterior lights is, even in daylight.
Nice tip. I will think about it. It is not "standard" airplane switch-ology, but it's cleaver. It only adds LED push button momentary switches and a few extra wires. COOL!
I originally rejected the push buttons because the STATUS of the system is switch position, ie toggle up or down, or some kind of label. "Scrolling" through different settings with a buttons is OK but too ambiguous. Your idea of LED indicators, some what solves that. However in flash I assume the LED would flash and would be distracting. I think that might be solved with a small capacitor to keep the LED steady even in flashing mode. The programing would require it to "Poll" the switch positions every second or two.
Mount the 2 buttons next to each other so they can be pressed individually or together with 2 fingers. A short press of either or both would switch the corresponding external lights on or off. A longer press (> 2 secs) would start either or both of them flashing. An even longer press (> 4 secs) would start fast flashing. This would enable quite a few combinations, e.g. steady on left with flashing on right, etc.
There might be some small timing issues, where you have to push and hold to get a change, but that is acceptable. You just have to be careful you don't get some unwanted combinations. It does not make sense to have one flash and one steady.
A single push button with two LEDS might work better, Push: Both, L, R, Flash, OFF ...... (repeat successive pushes). The two LED's would give status. Again flashing LED not a good thing on the panel of a plane, so that would have to be addressed.
This gets to be a little ODD in the airplane world. However indicator lights (LED's) are fine. For day-night operation it might need a dim for night, so the LED's don't blind you but day are birght for easy ID..
There is something about throw a toggle or turn a switch and it's done, that is easier and no LED's, but your idea is under advisement. The beauty of a micro is you can program it and change it.