I suggest that Games could be speed up by computerizing retreats. The computer automatically makes retreats by preset rules. This could be used especially in game variants, where perfect adherence to the original rules is not needed.
Retreat method 1 (Tischbein method)
The Unit is retreated to the province the computer deems "safest.' The computer gives one safety point for every friendly unit adjacent to the province, and subtracts one safety point for every foreign unit adjacent to the province. (This may end up in negative points) The unit is retreated to the "safest province.' If there is a tie, the unit retreats to the province which is lower in alphabetic order. One would expect a retreating unit to head to safety.
Retreat method 2 (Auto-Disband)
All retreating units are simply disbanded. This is easy to program. They can be rebuilt in the Fall.
Speeding up the Fall Build
Another thing that could speed up play is to merge The Fall Build turn with the Spring move turn. You would order new units and move them in a single phase.