PWM of voltage input to PIC - will it damage the chip?

[Amoque]

I think that you might easily do both with the same chip. Google "transistor as switch" this will allow all five LEDS to ramp-up from the same PWM output without issue (and the power needed to run them will not go through the PIC). You might use the same technique to tie several (or all) of the flashers together as well. This would be a good precaution to take regardless as there is a maximum output allowed from the chip. An I2C port expander would also provide 6 additional output pins (subtracting the two PIC I2C pins required from the 8 on the expander equals a net gain of 6) if you can spare the room.

The problem with an external PWM to run the PIC (if I understand rightly) is that it will be constantly resetting as the PWM signal goes to zero

Also in you OP you state your using a 16F1283, but in the schematic is a 12F683. Please clarify.