I'm afraid too. Most likely dependencies will increase as well as memory
footprint. But this is something we get regular asked on our boothes:
More intelligent auto completion stuff. Unfortunately this is one of the
things making the huge IDE so huge.

Yes, more capabilities or using less memory, sadly it will be "pick one" :)  Thats why having stuff plugin is important, letting you leave out the stuff you don't want.

Its good to get user feedback.  Are there any other useful inputs from your contacts with users that we need to know about for the purposes of these discussions?

I think this would need a more client-server-architecture as maybe
described in point 3. However, I'd like to have multiple Geany instances
working at same session. But I'm a little afraid of the changes needs to
be done for it.

Thats an interesting potential solution we need to examine.

> These are all big changes that don't fall into the current Geany mode of
> "light maintenance and extra features as someone implements them".  For
> big changes like those above however, a clear design and a planned
> process is needed to ensure that the big changes don't clash with each
> other and that they are not derailed by interim smaller changes.

I agree.
Also I think this needs to be discussed in a more face-to-face-session
than wiki or email.

That might be hard, Geany contributors are worldwide, in various time zones.  It can be done via email or wiki, I've done it more than once, with different countries.  It requires everything to be written in detail, which is painful, but that then leaves a record for later consultation so there is less "why did they do **that**" :)

Of course if you are offering to pay to fly us all somewhere nice (warm, beaches, good food)  for consultations ... :)