There's already connections between the FXTree and Softimage, so depending on what you need some stuff is already possible. Especially on the clip in/out section.
Way back in 2007 I was looking at beta screens of Toxic, at that point in time still bothered with a cumbersome database setup and connection to Flame etc. Toxic was slow, buggy and expensive and didn't add much to the already existing pool of AD compositing/editing apps of AD besides the new and exciting 32bit compositing and editing.
And at that point in time Fusion and Shake were still king of the hill, so another expensive app wasn't really picked up with enthusiasm
The peeps at AD never got Toxic to take off properly, so in the end it became the 'gift that comes out of your own pocket' as you're paying for Subscription anyway.
It's the same with Matchmover and ImageModeler, all three are dead products and haven't changed between the last three releases of Softimage/Max/Maya.
For your basic day to day compositing the FXTree works still wonderfully well, I use it a lot for jobs. For more extensive jobs, you can go for Fusion or Nuke, or, if you have a masochistic streak... After Effects