I can tell you are frustrated with this. I think you want more character space in the Prefix field. Am I correct? I didn't exactly follow your statement, "I request that prefix be deleted or used." Or do you mean as the title on each profile?
I'm sure you have read the Style Guide and the Name Fields for European Aristocrats.
The only thing I can add is when you put non-name data in the First Name fields, the result is that they names won't sort alphabetically. I think that in all the name lists and search results, for example, Sir William will appear in the S section rather than the W's. This is probably not a problem for Arbuthnots, but it would be very inconvenient for Smiths, Jones or other common surnames.
What happens if you place these titles in the Other Nicknames field? That is what I do with military officer ranks. But then, you should probably follow the guidelines for European Aristocrats as they have been carefully considered and selected as a "best practice" for WikiTree.