Improved building upgrading

Here's an idea for upgrading of buildings function:


Right now: you click on a building and click the upgrade button, it will start upgrading to the next level of the building


The improved upgrading: you click on a building and click the upgrade button - A new window pops up with a horizontal slider with 6(or more in the future) stops. The slider will be on the current level of the building. So lvl 1 building would have the slider all the way left. You could move the slider to the desired level, forwards and backwards. Allowing you not only to upgrade multiple levels and also downgrade multiple levels. Below the slider there would a list and an amount of resources required to upgrade/downgrade the building and time required to do so. Downgrading should be instant and should only show resources returned, while upgrading would show all required resources and time required.