One of the problems with an unbraced body is hinted at in the comments above. As it sits unsupported from within it will sag, twist, in general distort wherever weakest. The longer it sits, the more (and more intense) thermal cycles it goes through the worse it gets. Minor tweaks can be repaired with heat, relief cuts, section patching, whatever is appropriate for the kind/location of distortion. It comes down to a typical time/$/quality standards equation. If you have lots of time and little money you might be able to fix it, especially if your standards of fit and finish are "very flexible". If you have the ability to convert your time into money more successfully than most then turning that unsupported body into yard art might be a better move and find a well built body for the project.

As an unlikely aside, not all decent bodies have been supported by steel and/or wood. A few years back Harwood made both a roadster and coupe deuce body with composite inner structure. It just so happens the tooling for the coupe body is for sale on Craigslist in Portland right now. Disclaimer: this is not a recommendation to pursue buying the tooling as a solution, just a comment intended to provoke a HMMMMMMM.