My blog has thousands of short form posts and I very much like how they are presented. I just left it the way it was. I sincerely hope they never make me try to switch, but realistically I have to assume they eventually will.
I sympathise with wanting to keep the presentation. It was made in and for this context. It’s like reading an old magazine, you get so many extra clues about the context from the design. If a magazine does a redesign, it only affects the issues going forward. In my ideal world, blog redesigns work the same way.
I’ve done my share of maintaining and archiving older websites, where I tried to keep the design in place while updating the underlying infrastructure (or converting it to static HTML). The one thing I would sometimes change is to ‘zoom in’, multiplying all pixels in the CSS by a small amount, because the web moved to larger text sizes and screens, so older websites tend to look tiny.
Granted, I don't know how WordPress works, or any if its technical circumstances.