You could always substitute ordinary-character combinations for special characters - \"e\" or \"ae\" often works for the \"AE\" ligature, and the crossed-d - well, I dunno, dh, dth, th? I don\'t really know what sound it makes. Umlauts can usually be represented by appending an e - oe, ue etc.
This also makes names more easily converted to a mental \"sound\" if people know what sounds the characters make.