FWIW, I think the Clip name field works like that when multiple clips are selected. 
 

Soundwise
4. The best part! Synth Chains that work like FX chains. That is users can add several single channel synths like RPro, RS, DPro etc., assign each to particular MIDI channel, create macro controllers for synths' parameters.

I like all of your suggestions, but, you're right, synth chains are really appealing.  Unlike FX chains, I envision them being chained in parallel rather than series, but the chain metaphor is still a good one.

Soundwise
2. Display patch name next to synth name like this:
 EDIT: This may not work with non-CW synths, so instead of displaying Patch name it better have a name, synchronized with corresponding track, e.g.
Rename Track1 -> Bass and this change is reflected in Synth Rack, and vice-versa.

I like to think of the Synth Rack as holding synths independant of what they might be connected to, just as if they were hardware synths.  I like adding a synth to the Rack, then constructing and connecting any tracks to it as needed.  In this case the patch name would make sense to me, if possible.  I know some people think of a track as a synth (when it's connected to one), in which case the track name might make sense to them, but I don't like it.  The simplest solution is just let everyone decide how to label it in the Rack, as with tracks, but with no synching of labels.  The synth icon can be used to see which synth it is [why doesn't Rapture have a synth icon ?].
 
And I'm all for being able to change the order of the synths in the rack.

Paul P
I like to think of the Synth Rack as holding synths independant of what they might be connected to, just as if they were hardware synths.  I like adding a synth to the Rack, then constructing and connecting any tracks to it as needed.

I see what you mean. My point is, if a synth is used for one instrument, we need to be able to find it in the rack easily, especially, if many soft-synths are used (granted, tracks are named properly). Syncing synth's and track's names can be very useful, if the synth is single program only, like Z3ta, RPro, etc.
 

Paul P
I know some people think of a track as a synth (when it's connected to one), in which case the track name might make sense to them, but I don't like it. The simplest solution is just let everyone decide how to label it in the Rack, as with tracks, but with no synching of labels. 

Can't argue with this. But at least a synth in the rack needs to be highlighted somehow when corresponding track is selected.

Excellent post!
 
I could add the following things:
- when the synth rack is docked right, the on/off power button of each synth never appears. Why?
- sometimes I want to create a new synth very similar to another one. Then a drag and drop copy (with a '+' symbol when you're holding CTRL) would be great!

You got my vote too. Ref. point 2 I would also like to see the track number corresponding with a given synth.

Yes, the track number thing is important.