I know that's not what the upgrade means, just saying it's now possible to implement it - for example, in campaign rules, everything starts off without any upgrades, then after each battle, you earn vp's or xp's which can be used to purchase upgrades to use in future games.
Models can be killed, weakening your crew, or eventually growing so big they get on the radar of the big fish out there.
It worked for Blood Bowl and Necromunda, and Malifaux is the perfect model count for this kind of thing.
I'll have to look at this WC5 - any ideas hwere I can find it?
Also, no idea about Mordheim - never played it or seen it unfortunatley.