Thank you all for the useful posts.
Special thanks to Peter for the visual. A picture says more than 1000 words .

First some clarifications:
1. I do not plan to use the Märklin standard control boxes (7272 et.al.) but instead buy non-Märklin electrical switches.
2. I do no longer use any M track. It is all C now for the moment.
3. For the moment I control everything digital with one MS2 but I plan on buying a CS2 so that is what I am planning for.
4. All my old analog locos will be put away or sold. I only run on FX or MFX locos now.

Having that said, I will try to attach some images.
As you may note, I am not an electrician (more than on a hobby basis) but I hope you can understand my drawings .



Please feel free to correct me when I am wrong or otherwise comment on anything.
The "Analog bypass" picture to the left is exactly the same as Peter drawed but omitting the track power.
In my opinion fairly neat but have the "hand-of-God" - drawback mentioned by Peter and James.

The "Analog to S88" picture to the right I hope is the way to handle the s88 way that was described by Peter.
I also clearly see the benefits from doing this.
The only donwside I can come up with is the cost of the 6088x (which should not be neglected as the switchboard grows).

Now to spice things up I would like to add turnout indicators to my home made switchboard.
The pictures below should be substituted instead of the analog switches in the pictures above.



First: The lamps will actually be LED with safety diode and resistors in serie but for clarification I only drew lamps.
Second, the Light connection "L" can be connected to the track power "B" if I am not using an external light transformer.
Hmm... Wait a minute. Can I do that? As I understand it I cannot use a common gound from the CS2 and an external Light transformer, right?
That means I have to split the ground return for the lamps and use the switching part of the relay go to the red "B" connection instead, right?
The "Analog indicator" to the left uses a standard relay to handle the indications and in the "Digital indicator" I draw a k84 to do the same job.
I will then set the same address on the k84 as on the corresponding k83.

The upside of using the Analog version is:
*. Cost. For some reason, the k84 cost 3 times the k83. Why is that? As I see it I can achieve the same functionality with a k83 and four relays or just four relays from the k83 connected to the turnout (demanding some more cables though).

The upside of using the Digital version is:
*. Is there any? How have you done to indicate turnout positions on your switchboards? Or are you all using PC screens (except James)?
*. Edit: Yes. I believe there is. If I just use a relay on the manual switches, I will only get the indications of the analog movement. If I on the other hand use k84 (or k83+relay or connect the relay directly on the k83 on the turnout) the indicator will change indipendent if the turnout was operated by the analog switch or digital command.

Now, to press it one bit more I am currently only occasional building temporary layouts on my floor.
Still, I like to operate my trains digitally and would like to switch my turnouts easy.
My plan is to build a manual "module-based" switchboard. Each module is hex-shaped and will hold the components shown in the "Analog indicators" picture.
These modules will be placed in the switch board box depending on the current layout and connected.
For everything to be as easy and neat as possible, I would not like any cables on the floor (if possible).
My plan is therefore to use 74460 digital decoders under the ballast on each turnout and 6088x in the switchboard box.
Each module will then occupy 2 inputs on the 6088x encoder.
Edit: I also plan to use some k83 in the switchboard for the relays connection so the indicators will switch indipendent of how the turnout was switched.

In the future, I would like to have a permanent layout so all this is also tests for that.

All comments are welcome!
/Magnus (tyrre)

PS: Sorry that the image below shows twice but I do not know how to remove it .

Edited by user 01 April 2012 10:19:07(UTC)  | Reason: Missed the upside of using k84...