If there really is an advantage to having an assistant platoon leader, what would be the matter with making him the RTO also? Well, other than the obvious jokes that will ensue about how many officers it takes to operate a radio. He can learn quite a bit from following the platoon leader around. He can also learn quite a bit by always monitoring the net. It also keeps an enlisted man available for duties within a squad.
The purpose of the A/PL for a new 2LT to learn "the ropes." Initially, that may be following the PL everywhere they go. However, as the 2LT develops, the PL would hopefully begin to entrust him/her with leading sections of the platoon, like leading the outer cordon on a small platoon level cordon and knock.

With "vehicle-centric" operations and with the miniturization of electronics leading to the smaller "brick" SINCGARs and now the MBITRs, I do know if there is a need for the traditional radio humping RTO. However, with all the digital systems organic within a platoon now other than the radio, a Signal MOS Soldier adds value as being the hands down SME on those systems.

I described the Signal MOS Soldier as an RTO. A better duty description would be something like "Digital and Communications Systems Specialist" and his realm would encompass radios, FBCB2/BFT, PLGRs/DAGRs, and any other mission related communications or computer equipment is carrying like toughbooks and digital cameras.

When talking about the small radios like the MBITR, I do not see a reason why both the PL and A/PL would not both carry and monitor them, even if the A/PL is still in the "follow the PL" everywhere stage.