All right here is my proposal: a refund is limited to a percentage of the resources it took to construct something, say, 30%, multiplied with the current health status of the object, i.e. a ship at 60%health gets 20% refund. all refunds are tied to a condition: ships must be withint he perimeter (30m) of your own dock. Outside that area there is no refund. siege engines must be on your own territory, no refund outside. buildings are more complicated: some should not give a refund (e.g. palisades, walls, towers), others only give a refund if not under attack and fully owned, and - possibly - if one own unit is present in their vicinity (radius TBD and the whole thing to be tested). Deletion becomes a teardown: the building loses health over, say, 10 seconds, the resources arrive at the end, and enemy damage cancels it.  I'll adapt the mod and test it first before posting.

OK, point taken - how could that be addressed? Should we introduce steps and/or a cap, like 0% finalized- 100% refund, up to 70% finalized - 30% refund, more than 70% finalized - no refund anymore. Deletion after completion - 30% refund. Would that work for you?  Currently no salvaging of destroyed buildings exists and they can be immediately deleted anyway at the moment. Requiring units (no siege engines) to actively destroy own buildings woud prevent doing that to a whole group of  buildings at once already. Would you really want to use valuable units to destroy that one storehouse that's not needed anymore jsut to get back, say, 30 wood? For me this could be an emergency aspect to get more resources if none is in reach and no bartering is possible anymore, e.g. after a devastating attack of your enemy. Of course, but for gameplay and simplicity I would possibly tend towards the same level of resource refund (we could use the same mechanism).   But isn't that a contradiction? If it shall be ultra-fast (scorched earth tactics) it cannot be queued as this would take too long. 

Did a total review and refactoring of the user interface and functionality. Hope it is better now. I am placing the python code and new screenshots in the original post on top of this conversation. @Asher I'd love to have  your comemnts - please have a look!

Also, if anyone interested know how to animate, we are looking for charge animation (strike while moving) and staggering animation. 

No worries.