Then maybe the way to go is, applying for the reentry permit - remember you should file no fewer than 60 days before you travel- and use it for the 2 years validity and on the last year, don't renew the permit, just return to the US before the 6 month mark abroad.
You can actually file now and request for the permit to be sent to the embassy/ consulate in the city where you will be in Germany.
Except for the hassle it would be to travel back to the US in case your ROC interview is scheduled, you should not have issues.