Second idea... don't give up on a tadpole. The front boom of a tadpole is a really simple part that a welder could easily make up a hitch version. You could also maybe make something that attaches to the mast for the front derailleur. And she's far less likely to capsize you than being up high on a granny trike.
Surly makes a hitch for their trailers that I just cannot figure out from photos. But it seems like you could use it for this.
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Genesis 49:16-17