If it's not to be read, just use Good/Better/Best and you get what you are looking for (low 30% unique).
If a human being is going to read these, just tab through every other word and select one or two replacements that make sense. You can do a 500 word article in about 15 minutes this way giving you about a 60-75% unique score according to TBS. It sucks to do but it gets the job done for sure.