I imagine that from an operating viewpoint, mixed MU with the E44 leading might have been preferred, given that electric locomotives were often operated right up to the adhesion limits, and in 1960 that was probably better achieved by manual control of notching than by any automatic means. The E44 had much higher power per axle (and per ton of adhesive weight) than the diesels of the time.
In terms of control system complexity, from least to most complex, I’d postulate the following hierarchy:
1. Equipping the E44 to control trailing diesel locomotives via the customary diesel jumper;
2. Equipping the E44 to be controlled by a leading diesel via the customary diesel jumper;
3. Equipping a standard diesel to control a trailing E44 (and to be controlled by a leading E44) using the E44 jumper cables.
Re the E44 auxiliary functions, remote control of control switch reset might have been desirable. Possibly this could have been done by the diesel ground fault relay reset trainline. Except I don’t think that that function was trainlined generally back in 1960; it appears to have been something that came in during the mid-1960s or so.
Also from an operational viewpoint, if you had a fleet of electric freight locomotives that it was desirable to supplement at times – say for peak seasonal movements – with diesels drawn from a larger pool, then it would probably make most sense to leave the diesels in standard condition, and modify some or all of the electric locomotives for trailing diesel MU operation.
I also looked in Middleton (“When the Steam Railroads Electrified”). The several paragraphs on the E44 made no mention of trailing diesel MU capability. On the other, that the Virginian EL-C could MU with the motor-generator locomotives was mentioned:
Middleton p.202 VGN EL-C MU.gif
I’d say that Middleton was generally a reliable and accurate author (well, except about the origin of the 2-C+C-2 wheel arrangement). The “no mention” of mixed MU in the E44 case is not “proof negative”, so as to speak, but I’d be surprised if he had missed such a feature.
Cheers,