Hi Tkins!!
The trees are new to me, so i shouldnt comment too much, as i dont want to mislead you.
However, my guess is you can create a new tree, i think it will use the same layout and the researches that you want from either of the other three races you want to keep, or new researches. One of the modders on Wincustomize has a mod that adds more levels to the trees for all the races, instead of only one or two or three levels, he increased it to like ten levels for lots of them.
Haha, that is alot. Take a look at his mod if you can, and open it up in notepad to look at the way he put it together. Check the playeradvent.entity playertech.entity and playerphase.entity to see those entries. Check the research items in the gameinfo folder to see their position and a little of how they work. Most dont explain what they do inside the file, that is located in the infocard but it is interesting. 
Anyway, i will have to turn you over to someone much more experienced than me, as i am just a newbie at this, but thank you, and oh... i got the phase stabilizers for the advent and the tech added in my Songs of a Crystal Sun 3.4 mini mod that i put on filefront, the url is:
http://hosted.filefront.com/TealBlue
Take care and have fun, let me know how the tree research goes!!
-Teal