Timestamp Calculated Date Properties

I would like to have a property type like a calculation that I can use to set a timestamp based on another property.

 

I know, I can do this easily witha workflow, but workflows break pretty easily, or can be changed, and there's a max number of workflows that we have to respect. Our "set timestamp workflows" are starting to significantly add up and the limit is getting close...

 

This would be particularily useful for setting dates of different stages in the lead process as well as dates of certain key actions that a lead takes.

 

Thanks!