It is an interesting topic. There are a variety of things you can do if you have all the strings you mention. One very noticeable fact about the ensembles is that on a unison, it does not necessarily increase the complexity or expressiveness if you simply layer Chamber with Appassionata, or Orchestra with Chamber, etc. This is because smaller ensembles can make a larger ensemble sound smaller itself.
However, if you layer a solo string with Appassionata (or any of the other ensembles) it increases the espressivo quality a lot. The solo must be very soft and reduced in dynamic range so it drops out while the large ensemble gets louder. That can be done by turning the dynamic range slider down. Also, they should be significantly humanized with a different preset than the ensemble.
Another good use of the smaller ensembles is for larger divisi sections. I have found that orchestral is a good divisi for two-part divisi on Appassionata, and Chamber is better for three parts or more. Even though the numbers of players may not match exactly, in actual sound it is very close to real divisi sections. You can always layer in solo as well if you wish, including a second transposed solo violin on second violins. This, if used with different humanize settings, can be very complex and expressive. Also, the changes in timbre caused by shifting from Appassionata to Orchestral or Chamber for divisi are almost perfect.
All of this does not mention the Dimension Strings, which I feel are the greatest thing yet created for sample strings. Because they can be used by themselves all together, or in ANY COMBINATION of individual players among themselves or with any of the other ensembles. You can imagine the number of possibilities of combinations this creates, especially since they are incredibly expressive and varied in their sound, just like the real players who recorded them.
On MIR setups, I have basically tried to place the smaller groups where they would be if they were divisi of the larger group, simply laid on top in two or more parts of the larger ensemble. If it was solo, I simply placed the player where he would actuallly be sitting among the other players. It is probably best to make each instrument in a different position.
One other thing - In order to deal with the massive amount of CPU and memory that this approach entails, since I don't have the largest computer system I have sometimes done a second group of strings after freezing the first. With Dimension, this becomes necessary unless you have the largest possible RAM. I have only 24 GB so I ended up doing second run-throughs with a different ensemble that was humanized differently and placed in slightly different positions on the stage. You can hear some of this stuff on the Vertigo demo I did, which has a lot of layered strings including Solo, Appassionata and Dimension.
