RE: IDE

[Drew Adams]

> Not sure what you are saying.  Is it that a region with two ends is
> not enough, and we need a list of regions?  If so, I'm okay with
> that, and I don't see any serious obstacles to implement that.

FWIW, library `zones.el' provides that, along with various
commands for defining and using such multiple-zone "regions".

http://www.emacswiki.org/emacs/Zones

You can sort, intersect, or unite zones; narrow the buffer to
a zone or select one as the region, (un)highlight zones, make
a list of zones persistent (re-created with a bookmark), or
use incremental search across it (overlapping zones in the list
are united for this).  You can name lists of zones and switch
among them for different multi-zone operations.  You can
associate arbitrary information with a zone, which is otherwise
just a pair of buffer positions (e.g. markers).

This does _not_ provide the feature of having zones that are
in different major modes.  I agree that that particular
feature is sorely missing.  There have been various attempts
at providing it, but I'm not aware of any that has been really
satisfactory in a general way.