4-5th century tunic idea for a germanic warrior...

[Flavivs Aetivs]

The Coptic Tunic evolved from Roman, not Germanic fashion. Your best bet for a middle point would be the Dura-Europos Tunic:

[img width=250]http://www.medievaldesign.com/restricted/immagini/1grande_9994.jpg[/img]

This is mine:

[img width=250]http://www.medievaldesign.com/restricted/immagini/grande_5969.jpg[/img]

Here's one based off the Isla Rizzola Mosaics in the Late 6th/Early 7th Century:

[img width=250]http://www.medievaldesign.com/restricted/immagini/1grande_1845.jpg[/img]