Bringing up an old, but important, thread.
Some years ago, I went to the Tillet B5s, and think they are ideal for my use case.
But I have recently seen some modified stock seats that have made me reconsider my original take on them.
For example, a close look at Rumbles' car-- which uses the stock seats as a foundation-- shows that they can be made both attractive and functional, improving the looks and fit. I recall that he ended up trimming the wings, and even made a back, so the seat looked like a traditional seat, with a front and a back. All in all, a very nice job, and with the unique approach to upholstery on an SLC, it looks every bit the part for a supercar as well.
I briefly considered the idea of modifying the stock seats, but thought it would be too much trouble, and that the results might be unsatisfactory. Bill's car shows that this doesn't have to be the case.
There are other cars as well, like Stu's car in Australia, which have been nicely upholstered, and look great, though I don't know if they have had the wings trimmed or not.
Once you commit to modifying a seat, previously insurmountable problems like an incorrect headrest angle when fully reclined can also be addressed with relative ease.
The bottom line for me, at least? The stock seats, both the original and now the new seats with shoulder belt holes, are a reasonable foundation for some drivers as-is, and can be modified to meet the needs of taller or wider drivers with a just some creativity and thought. And they can be made to look pretty good as well.