Hi Ms. Hamilton et al - here comes another of my inelegantly formed arguments -
I don't believe it's necessary to think in terms of sidereal and tropical regarding the Babylonian system, because I am not that sure that they used a sign/ruler zodiac anyway. Take a look at Gavin White's book 'Babylonian Star Lore' and let me know what you think. I think they were more concerned about the groupings of the stars, and such things as which of the three 'paths' were in some position relative to the rising and setting stars (including the planets). I know that this does not sound like much of an astrological system, but if you think of all the possible phases of the planets, the swift movement of the Moon, the declinations (which were probably a factor because it would help determine co-rising and setting stars and the degree North and South of due east at which the Sun would rise, etc.) and other things they used, they probably had more than enough to satisfy a very fate conscious king (as opposed to a very scandal hungry merchant's wife, who would have had to be satisfied with sheep entrails - astrology would have been the property of the 'cultural elite' I guess).
Nevertheless, I have, for a long time, considered precession correction (excluding the Indian dasa systems) the only reason to use a sidereal zodiac. To me, the system of signs was based on the solstices and equinoxes, not because of Europe's seasons, but because they are the pivot points of the Sun's apparent path. The reason I think that the apparent path is so important is because, as in Plato's Cave, we see the shadows - the analemma is how we see our course through space. The points at which the apparent path of the Sun and the orbit of the Earth converge or are at their limits of separation are functions of obliquity of the ecliptic, right ascension and declination. Just like plotting a sine wave on the X and Y axis - the equinoxes would be the places where the curve crossed the Y axis, and the solstices would be the positive and negative extremes on the X. I believe that the signs show the effects of the Sun's rays from the solstices and equinoxes, rather than to describe the effects of 12 rectangular batches of stars - in other words, Virgo is like it is because it receives a ray from the goat-horned one and the crab (2 of the 4 Trigons) etc., not because Spica is somewhere inside the virtual rectangle.
The old 8 house scheme, in which the heavens are divided by time, rather than geometry, gives us a sense of the planetary position relative to the horizon and the meridian of longitude, and their midpoint. This type of divisional scheme does not consider the declination cycle of the Sun as being a linchpin of the system - it is more like a proto-Gaquelin-sector expressiveness measurement (Indian astrologers call this Kendra Bala). Consequently, for this design, the 'quality of time' has nothing to do with geometry, it is all about local and apparent celestial phenomena and planetary expressiveness.
In a scheme like this, essential dignities based on the ecliptic really aren't essential are they? In other words, this view is all about the background of the fixed stars, relative to the appearance and disappearance of a planet, or its relationship to dominant (angular) positions. I think this is where Fagan was going when he began to abandon the zodiac. Nevertheless, considering the methods of progression and such that are used in this system, a totally apparent sky/planet centered system is neither inconceivable nor inadequate to symbolize events in our lives.
I do not discount the viability of the sidereal zodiac, nor the techniques used by either eastern or western siderealists. I use them and understand them myself. I believe that these are different systems, different schemes, developed with an internal coherence of their own. I do not believe it is necessary to expect the sidereal "signs" to act the same way the tropical signs do. In fact, I believe that the sidereal 'zodiac' is just the tropical zodiac based on the time of convergence, when precession held the vernal equinox close to 0 Aries. I think that the genius of the tropical system is in its integration of geometry into a system based on the relationship between the Earth and the Sun. I think the genius of the sidereal system is the integration of the 'mundane' sphere and the planets into a useful system of omens based on the relationship between the individual, the Earth and the heavens. I don't think the sidereal system needs a zodiac analogous to the tropical one, any more than the tropical zodiac needs a 13th sign.
Some time ago I tried the Hellenistic time-lord systems in the sidereal zodiac to see if I could get anywhere near the level of accuracy that I did with Dasa systems. They failed. I started running them in the tropical system and, yep, they worked fine, and are working better now that I am learning more about the system of Hermes. Plus, the Hellenistic authors explain little things, like why the minor periods of the planets are what they are. I get more from studying these methods than "it's in the book", or "it's what the guru has blessed us with" when I ask why something is as it is. Do Narayana Dasa in the Tropical zodiac - I think you'll be surprised.