I anticipated the voltage drop problem but without a specification for the solenoids it is difficult to see how much it is likely to be. However, to mitigate the problem I used a comparator and increased the supply voltage. Increasing the voltage makes the voltage drop in the wiring less significant. You have again dropped the supply and used an op-amp. If anything I would have done the opposite and run the comparator and resistor chain from a higher voltage.
Nevertheless, I think you would agree it can be much simpler than originally proposed!
Brian.