Weight for units have one drawback it need some changes to UI, my version will reuse already available UI.
Another is that if we use values as `22` or `41` you could end up with situation that you left only `20` and you could not fit easy another unit.
Unless you already have proper weight set for all corpses, like I do : )
EDIT:
I just don't think trying to repurpose soldier number limit will work here. We plainly need a separate limitation (like weight), due to soldier spawn points being immutable. Weight limit makes a craft take a designed number of soldiers
or less; tweaking the number of slots a soldier takes makes a craft take a designed number of soldiers, or less,
or more (if it was designed for "large" units), which will cause trouble.
As for the GUI, the equipment pile indicator (the little "guns" that appear in the craft menu), can be repurposed to show weight if that option is used. As in, 100% weight is represented by all slots filled (make it dynamic instead of linear).