Another basic feature I would like to suggest, which I also plan to use personally. Would it be possible to let units spawn other units upon death please? I'm imagining a definition among the lines of:
<spawn-on-deaths>
<spawn-on-death>
<unit type="my-unit"/>
<count value="5"/>
<health value="25%"/>
<probability value="50%"/>
</spawn-on-death>
</spawn-on-deaths>
This would allow useful mechanics such as: A technician emerging out of every catapult / ballista / battle machine that's destroyed (the operator walks out of the wrecked device), drake riders turning into summoners (implying the drake died but the rider survived), workers emerging from castles that have crumbled, and more types of logical unit conversions.