In the same way you have E signature for Form 8879, ProSeries should add electronic signature of the final accepted tax return to be signed by all parties (taxpayer(s) and Preparer).
As everyone is going paperless, it would be a nice enhancement to allow the taxpayer and the preparer to have a signed accepted PDF of the final return.
If a taxpayer applies for a mortgage and submits the tax return with Form 1040 unsigned and Form 8879 signed, I expect the taxpayer will eventually have to sign the tax return to get the loan. The E Signature copy Form 8879 is unsigned by the Taxpreparer.
So, in the end, I have an unsigned PDF of Form 1040 and Form 8879 that is signed by the Taxpayer but not the tax preparer. Lots of loose ends.
I think the Tax Preparer should also E-sign Form 8879.