Not exactly what you want to do, but I recently updated a mod to have affixes for all uniques, in my case only rare ones. Here they always drop with both, as intended. Does not really help you, I know.
As for items potentially not dropping with higher levels, you would need to set the MaxLevel of e.g. containers to 100. The Nemesis chests for example have a MaxLevel of 200, so you would need to lower that. Probably not a full fix, though.