I'ld go with it.
Timeline wise you are arguing a mixed MLVW purchase in the early 80s to replace the old Deuce and the M818 series five tons.
You're right about the increased tactical versatility of a five ton. For the most part the US Army only employs the M35 for light company level logistics (stores and kitchen), unit maintenance stores and a few light signals shelters. Most of the specialized work such as engineer stores, signals shelters and such is the responsibility of the five tonners. Interestingly the German Army employs a 5 - 7 - 10 ton family concept for cargo and specialized work.
Canadian Signals ran into this problem during the TCCS program with some SEVs, finding the MLVW too little truck and the HLVW too much.
Look forward to seeing what you com e up with.