Your approach seems about right to me, if your layout can accomodate 8 coaches.

On my small layout I have to be even more selective and usually represent such a train with 5 coaches; two blue/beige 2nd class, two red/cream 1st class, and a red/cream dining car.

In fact I can represent such a length of train best with 24cm coaches. With 27cm coaches I can still do it but the station loop is a bit short for it.

Here is info on the prototypical IC Hohenstaufen consist - see PDF: E.g. 103 electric loco + 3 x 1st class + diner + 7 x 2nd class.
ic_hohenstaufen.pdf (89kb) downloaded 46 time(s).
Source: http://www.welt-der-modelleisenbahn.com

The IC Adler in the middle of his career is more MRR-friendly - see PDF: E.g. 103 electric loco + 3 x 2nd class + 1 x 1st class.
ic_adler_1.pdf (92kb) downloaded 30 time(s).
Source: http://www.welt-der-modelleisenbahn.com

IC Adler pic:


Here another contender (unfortunately no further info found) - see pic:

I agree with Glenn that eight is enough for a long passenger train. On the ETE modules we have the capacity to run longer trains than that before a train has to turn a corner. But realistically, eight is a very long train visually, and with many more cars than that operational reliability goes down because of the pulling dynamics of the weight of the consist (just like real life!). False uncouplings increase as well as the possibility of derailments on curves. In addition, starting the consist too fast can create derailments as well, particularly if any part of the consist is on a curve.

Not many home layouts can run 14 cars in any sort of straight line, and in fact I don't recall seeing any layouts with the station capacity for such a train.

On my layout in progress, in one station I can have six cars comfortably behind a locomotive. This is not my ideal, but seems "long enough" when operating.

I remember being frustrated in my early Marklin days with the passenger sets that would come out, having only three or four cars. Sometimes there would be an extension set, but not often. Of course when I thought about it, I realized that these were "layout size" consists that probably satisfied the vast majority of customers. Now many sets come with six cars as well as having add ons. For module operation, this is ideal.

Also, there really is a prototype for everything, and short consists are relatively common.

In this context, a short IC Oldenburg—Bremen—Hannover in good company.

Slightly off-topic now: Approach by the late MRR layout designer John Armstrong - see screenshot.
;o)