No tricks are necessary; the script just has to wait for the SE4 process to exit. Most exec functions in programming languages have a way to do that directly. Dunno about batch, but its a 3 line python script (plus the import os line). I forget exactly what the command line parameters are, so you'll have to put the exact commands in. Assuming you have python installed, set the range to the number of turns you want to wait, save as something.py in the se4 folder, and run it (DOS prompt is easiest way).
Code:
import os
for i in range(20):
print "Executing turn " + str(i+1) + "..."
os.spawnl(os.P_WAIT, 'se4.exe', 'savegame', 'player', 'password')