Hi Tobias,
Nothing standard, as far as I know.
The basic "tools" exist in GTS for printing the forms, so you could re-create them in GTS. But not ALL of the proforma data, and very little of the Delivery data, is transferred to GTS, and of course the structures and fields there are very different, so you would need to do a lot of work to get the forms working again.
As for your question about launching the ERP document from GTS; I think it sounds quite reasonable. You could create an entry in the Idea Place, but bear in mind that GTS can work with different feeder systems, not only SAP ECC.
Regards,
Dave