Short answer: Yes. Will Nokia allow you or someone else to create a tool that will permit the creation of such images. Short answer: No. Will they allow the use or distribution of said custom images should they be created. Short answer: Epic Hell No!

So yes, you can write a tool to do it (nothing currently exists that can do this, but it shouldn't be hard to write a tool that more or less mirrors your entire drive into an installable flash file) if you want, or have someone else do it, but don't expect the project to live long before Nokia pitches an epic sized C&D at it. And I wouldn't really blame Nokia if they did. All corporations these days are getting super anal about anyone doing anything with their products without the expressed blessing of corporate.

Sure, we produce a lot of FOSS software for the NITS and the 900, however, that work is corporately blessed. Creating an app that can create custom flash images however is not, nor is editing existing images to create your own custom image either. Now if Nokia corporate wants to give its blessing to something like that, I know we'd all welcome it. But I seriously doubt they would, for several reasons.

A) There's risk that bad or compromised images could get on the web and be listed as "official" images of Nokia, and thus said compromised users would blame Nokia even though it's not their fault.

B) The custom images would be outside of Nokia control, so when new changes came down, Nokia would not be able to force the needed updates (Ie, security, features, etc) to the images that is required. And thus they would get blamed.

C) A poorly compiled custom image could fry the device, thus resulting in loss of money for Nokia due to warranty repair or bad press.

And there are a hundred other reasons they don't allow said things such as custom install images to happen. Most of it is corporate CYOA, if you get my drift. And honestly, in our "sue at the drop of a hat" society, I don't blame them. Fix our environment of lawsuit overload, and most of those kind of problems would go away. The only problem with that idea is you'd have to kill all the lawyers first, and we all know hell will freeze over first before we rid ourselves of the plague of lawyers.