Current source with multiple "taps" for driving different LEDs
I'm all for component parsimony for aesthetic reasons! 

Here is your tapped current source.







simulate this circuit &ndash; Schematic created using CircuitLab

When just D1 is switched on, its current is defined entirely by R1. Here with 1.2v across 10 ohms, it's 120mA.  As D2, 3 and 4 are off, R2, 3 and 4 transmit the voltage generated by R1 directly to the ADJ pin, with essentially no voltage drop, given its low input current. 

If only D2 is switched on, then the drop across R1 and R2 controls the current, 1.2v across 12 ohms is 100mA. The same type of calculation will give you 75mA for D3 and 60mA for D4.

Obviously I'm using nice round number resistors here to illustrate the current control, you can use any values and any number of tap points for your purposes.

One advantage of the single current source is that if multiple LEDs are accidentally turned on, the total current is still no greater than the maximum possible defined by R1, a feature you won't have with individual current sources. 

This then means you can safely use a multi-output ground switching driver like ULN2803 (which is a darlington driver, I've shown FETs, you can also get FET-based ones). In the case of the ULN2803, it will switch 500mA at up to 50v per channel, but for dissipation reasons, not all channels 500mA at the same time. This tapped current source limits its total current if all channels are switched on at the same time.

There is a drawback, the current setting resistors interact, but at least in a systematic way. If you want to change the programmed current for D1, then you alter R1. I would be inclined to make R1 too high, and then shunt it with low power, higher value resistors to get to the desired current. However, the change in R1 will affect the current for all the other LEDs. This means that after any change, you have to re-adjust all LEDs at lower tap points. Tedious, but straightforward.