Ores and Settlement Upgrades

So I'm loving the league so far, but one thing that jumps out at me, and this has almost certainly come up many times already, is how some settlement upgrades require ores. Ores which can be snapped up by smelters, given that they share behavior with miners, smelting anything if their assignment is empty.

Thus, if you need to save up ore for an upgrade, you need to unassign all your smelters until you can, or they'll smelt your ore.

Suggestion and solution is pretty simple, just make settlement upgrades that require ore also accept bars. Then it's no issue, since that's the only reason to ever keep ore unsmelted.

Best current way is to only assign one or two workers to the smelling task.
They will lack behind with the work and by the time you've upgraded everything you can put up more.
This saves also quite a decent amount of gold over a couple of days