I Need to Cook Duchess Potatoes but the Oven Cannot go Above 135C or 275F Thanks for the view. This question follows on from this one (Why Did the Duchess Potato Collapse), I have now prepared the mashed potato with egg yolks and do not expect it to collapse. The piped duchess potatoes are now shaped on a baking tray waiting overnight for cooking tomorrow. Here is this times effort so far for reference:

I am updating my skill level from home cook to bad after the last post.
I am planning to cook these tomorrow but only have one oven that will be slow cooking / braising beef short ribs which will be set to 135 Centigrade or 275 Fahrenheit from approximately 0900 to 1400, aiming to have 14 served by 1410 and I can't change the temperature as the meat is the main part of the meal.
How can I cook the Duchess potatoes when I can't change the temperature of the oven and the recipe says to do them at 220 Celsius or 430 Fahrenheit for 20 mins to be served immediately?
Options I've thought of are:

Put them in with the meat for longer and accept they will take longer. This is my preferred option but when I reached out to family the response was that they may not brown correctly. It was suggested this could be corrected under the grill right at the end when the meat is removed and being served
Cook them at the proper temperature for the full time before the meat to achieve the browning and let them stand for four hours before returning them to the oven to warm them up again at the meat temperature.
Cook the meat and then turn the oven up at the end to cook the Duchess potatoes to their recipe (20 mins at 220C or 430F) while the meat stands, maybe returning it to the oven just before serving if the temperature drops.
Cook the Duchess Potatoes before and reheat in the microwave while serving the meat

I'd like to know if any of the options above are the correct approach or definitely not going to work or if there's an option I haven't thought of yet that's a better way.
As I've stated I haven't much experience in this area so there may be an obvious trick I'm yet to  learn.
You are missing an option, which is to let the meat rest before serving and bake the potatoes at the right temperature. Most meats, especially beef, become more tender if they have a chance to rest, as it lets the fibers relax. This is true of slow cooked meat as well. So, your best option is to take the beef out, keep it covered and crank up the oven for your potatoes. If you keep the beef covered or wrapped up in foil it will still be hot enough to serve.