Hmmmm would you rather have a miranda built from scratch... as per say in wrath of khan version... or one rebuilt, using the necelles and stuff from the gagrin tho?
From a kitbashing and development point of view, I'd say the rebuilt version would be a faster build for you.
And if you rebuild the Gagarin into a Miranda class, you'll be reusing names for textures plus parts, which means less blanks to develop, mapping is the same, and it'll be a common base to build from for almost any platform. So my personal preference would be a rebuild, it's quicker and takes less build time for you. But... I don't think that it'd be as clean a mesh as a build from scratch.