Have you thought about using one 4-20 mA input and 3 x 1 - 5 Volt in parallel with it.
It used to be very common to string 3 or 4 4-20 mA devices in series e.g. chart recorder, alarm unit, controller that's still a viable method provided the inputs are isolated from ground.
Be careful with this idea of stringing multiple devices off one 4-20mA source. The 4-20mA source may not have enough power or voltage to generate the current through all the devices.
I once saw an application where one level instrument fed 4 readings: PLC; Telemetry; Chart Recorder; and local indication. Everything was okay until the tank filled to near capacity. The level instrument simply couldn't push more than 16mA through the chain and the high level condition was not seen by the PLC. The tank overflowed, and the cleanup operation was very unpleasant.
You're recommending that everyone use extra pieces of hardware in every app till the end of time because you once ran across some guy who couldn't or didn't bother to read specs (and maybe even test them out personally)? Seems a bit of an overreaction.
The spec you are looking for is compliance voltage. This means the voltage that is available to keep the current constant in the loop. It's a question of loop resistance. 4 250 ohm (typical) devices in series will drop 20 volts at 20 ma. In that example the compliance voltage was only 16 V so that was as far as it could go with 4 loads. It would require a compliance of at least 20 volts to handle 4 loads. This lets you determine if it should work without getting the floor wet. For 250 ohm devices, simply figure 5 volts per device. If the current source runs from a 24VDC supply 5 won't work, 4 is questionable, check the spec., 3 and below should be OK.
