Are there any bicycle makers/manufacturers that powdercoat their frames?
Back in the day Saracen powder coated all their frames and.Raleigh have used a nylon powder coat in some of their better frames, such as the Max Cromo series. Many modern manufacturers use powder coat, a few with gloss lacquer atop it either as standard or as an option.
I'm a fan of powder coating and if done well by a skilled artisan can give results virtually indistinguishable from paint. However, that level of expertise is very rare indeed so on a valuable or historically significant machine a wet paint finish of some sort is the way forward, and I think our OPs frame would be best served with a decent paint finish.
Get the frame blasted by all means but avoid shot or bead blasting and pay out for soft media blasting of some sort, such as crushed walnut shell. I'm not a fan of chemical baths for stripping as it's difficult to remove the liquid from inside the frame tubes and over time it can compromise the new paint.
It's a lovely frame and I'm looking forward to watching the build progress.