I have read the link you posted and I'm still not clear on how you would end up paying ~50% and not be able to get it back.
If your ETF is "ausländisch thesaurierend" ("foreign accumulating"), declaring it will be a bit more complicated but not that hard. Would you mind explaining your situation a bit better? Maybe I'm missing something (and I wouldn't want to, since I'm looking into this topic myself at the moment).