I think making them slow but no stamina would be good, if cover and concealment can be deeper. Realistically, infantry should not be sprinting everywhere, they need to conserve energy for the fight itself (and if you need to get someone somewhere in a hurry, then give them a truck or half-track). Sprinting also realistically would make a soldier less combat aware, since they are more focused in controlling their breath than staying aware of his surroundings. Just a slower general speed would be good, encouraging the use of transport.
Having a good recon system designed for infantry would be essential. No helicopters or advanced optics to help recon vehicles, so infantry should be the most basic eyes and ears of a military. No more requiring a vehicle for almost every job.
Perhaps a "stance" system. Infantry can be set to a safe, normal, or combat stance. Safe stance, infantry will take the fastest route and manner to a destination. Normal stance is default, balancing speed with combat effectiveness, and combat stance slows the unit but makes them stronger in a fight, harder to see, and tankier during a barrage (since they are paying attention to surroundings, advancing tactically between cover and concealment, and maintaining a formation that would take as few casualties from light artillery as possible). This way, you want "Safe" stance on parts of the map not seeing action, setting up a defensive position fast. "Normal" stance when advancing with vehicles or support. "Combat" stance for very infantry-focused missions, or small unit missions.