Then you get right into the realms of design issues. An all-voltage electro diesel would be massive, complicated and unwieldy if it was to have useful power output on all modes. Think a 92 permanently coupled to a 66 for size, and then start thinking about how you'd control it all and distribute the electrical power to the traction motors.
The 73 is a wonderful little machine, but it's design trade offs are very noticeable, in terms of power output. On diesel it's not much more than a big old shunter.
Well this baby
http://en.wikipedia.org/wiki/EMD_DM30AC doesnt seem to be that big, it doesn't seem to be much heavier than other typical American diesel locomotives. It is however only third rail but the question has to be: how much does the transformer equipment actually weigh?
Either way, Isn't a big ol' shunter you actually need in an intermodal yard?
EDIT: it now appears the DM30AC is actually a Bo-Bo, which says something about the insane axle loads allowed in the US.
We really need the standard used to calculate Route Availability before we can actually work anything out though
EDIT #2: The
ALP-45DP seems promising, ~5500hp on electric power and somewhere in the region of 3500hp on diesel power, the question becomes whether or not it can be built on six axles without massively increasing the weight to the point where it cant fit in RA7. Judging by the weight of the
Powerhaul this would appear to be simply a design issue.
It would also appear to have its electrical system designed to manage all 5500hp on at 12kV @ 25Hz, this will more than double the weight of the transformer, which is quite challenging, it would probably be possible to build it to have (atleast diesel-equivalent) third rail capacity on the weight budget once this unneccesary fat was "trimmed off"