But perhaps this is a rather esoteric question, and not something that 
should be a primary consideration when designing the MIME user
interface. 

> But then there's the question of multipart/alternative and nested
> multiparts and how to compose those. That wouldn't be quite so easy,
> but I don't think it needs to be and I'm sure something could be
> figured out. Like possibly highlighting some number of adjacent
> parts with transient-mark-mode on and then hitting some key combo to
> signify that the parts are alternative or nested.

I'm against marking parts and then issuing commands.  :-)  I like to
enter commands to make things happen; not futzing around with the
cursor a lot, and then making things happen.

-- 
(domestic pets only, the antidote for overdose, milk.)
  larsi@gnus.org * Lars Magne Ingebrigtsen