Just have it so Formation/Squadrons don't exist before and after the battle.
Before each battle you can assemble your remaining dudes from your 20,000 points into formations (if there are enough left to form one). After the battle is over they become non-formation units again.
If a Vehicle dies its gone. If a Squad dies its gone. If a warlock attached to a guardian squad dies he is gone. Base it all off the individual unit listings in the 20,000 list.
Playing it any other way is going to create some very odd issues.
Last edited by rand0mnumb3r; 06-26-2015 at 09:23 AM.