We have a use case for this which I expect could be quite popular. We have several partner companies who send leads to us. We want them to be able to complete a form containing all the relevant information and have that create a deal which is acted on immediately. We do have a workaround with duplicate contact and deal properties plus workflow but we have a potential problem when a partner wants to input two leads for the same contact. I agree that forms should be able to use properties from any object in Hubspot. looking forward to an update on this one.