I would personally use 3 linear drivers and sequentially strobe them. You have a linear voltage that must be by definition less than the maximum current of the LED's and a window in which to process it. So separate the two and do each in it's own time. Provide the amplitude modulated information to an LED driver and strobe/enable the driver in it's time (data position) slot.
trying to PWM data at that level of precision would be quite an undertaking both in generation and detection... Assuming the modulation (voltage) is within the dynamic range of the LED. A 0 to 10 V signal would require "Some" processing first.
Bob