My take on a Queued upgrading feature

To cut to the chase, my take on the idea of queued upgrading would work like this:
All queued upgrading can only be done by the goblin builder. (Costs would be 5 gems per extra upgrade)
All resources would only be used when the upgrade takes place.
The highest upgrade you can queue to would be what is currently your highest building upgraded (ex; if you have a gold mine at level 14 your gold storage level max is level 16, you can only queue the upgrade to level 14)
Hero’s would be able an exception to this rule, due to max hero levels being different, since you could have a level 50 barbarian king, but a level 15 dragon duke at TH 16

It would definitely be nicest for those resource collectors, especially when you get a new one