Substitute e-signing

Hi,
Since the built in substitute function is not enough in case you want to use substitute users as e-signers is there any other way that it's possible?

Let's say you select person 1 as an e-signer of a document and that person is on sick leave.
If that person has selected a substitute user during that period, that substitute user can't e-sign documents but this is a very common scenario that we would like to help our customers with.
As is now we must update the document with the new signer and send it for signing once again?

Is there any plans on fixing the built in substitute functions since it's so limited?

Thanks
Admir