Stepping away momentarily from this project was a good thing. I came up with an "easier" solution.
I went for option #2, because (lack of) finances rule, and it was the cheapest alternative. I had already chiseled out the cavity so that the neck could be repositioned. Then I found another pickguard, which was like a revelation:
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I had been basing this build on a TELECASTER pickguard (the one on the left). The pickguard on the right is the one that was on the original guitar that used the acoustic sensor bridge I'm using now. The most obvious difference is that the left pickguard uses a single coil pickup, the one on the right uses a humbucker sized pickup. I do have a humbucker sized pickup that would be good for this project. The one that was in the original harp guitar neck position.

In this picture below, I put one pickguard on top of the other. I aligned the top edges where the pickguard touches the neck. Notice that the humbucker pickguard is about 1/4 inch shorter. JUST WHAT I NEED.
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Here's what it looks like roughly positioned:
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I drilled 4 new mounting holes and attached the neck to the body. Intonation will be correct now. Here's a picture showing the neck aligned to the body. I use the two outer strings as straight edges to align things up correctly.
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With the neck mounted, I check the alignment of the bridge pickup. It's perfectly located beneath the strings, so I can attach the pickup to the body now.
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The new pickguard still needs a bit of work to fit properly, so I trace the first pickguard shape to the new one.
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Then I held the pickguard in the vice and rrough cut it with a copy saw.
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Here's the area that may need work in the future. I can live with it until the warmer weather, when I can cut, sand, and paint it when it's more convenient. The pickguard "should" be centered on the body. You can see there's a lot more wood to the right of the pickguard. Cutting this out will make the upper access wider, and also lighten the instrument a little.
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Next step is removing the single coil pickup and soldering in the humbucker in its place.