Set available for use date in asset

Dear All,
i am exploring asset module in erpnext. i have one scenario to start depreciation

basically when we purchase an asset it goes to a location and asset will be in draft mode.after we input availabe for use date and deprecaition schedule will be calculated(this is what i understand from erpnext)

my requirement is below

An employee or department request for an asset and company will purchase this asset ,the asset will come warehouse (store) first then transfer this asset to employee or department

here i have to set available for use date based on date the employee or department received this item

now it is mandatory to set available for use date before submitting the asset

please anyone suggest me a workaround for this