this is not as easy as it sounds.
images are linked as is in the frame and only very "general" formatting can be applied to them in scribus.
for the text, you often do very fine changes, sometimes with formatting that are not supported in the external application that has created the text.
of course, the feature would be very welcome, and optionally storing the text as external html + css would be a first step.
the first big challenge: finding a library that parses css in an adequate way.
not something easy, but if somebody volunteers to work on it, we will not stop her!