You could use a deasal engine if the unit was small enough as walking pillboxes or mortar support. Though you would like the size more like >>629484, something you could park in your back yard or hide in a parking garage.
> If we train and treat our soldiers like professional athletes, each one would be vastly more effective, more capable of carrying armor that protects the entire body.
With the the US military in mind, don't care about making grunt super solders that will need more than a decade to perfect but are happy with a armored truck that will cost them less in the long run.